A Brief Background to Modern Philosophy

A Brief Background to Modern Philosophy

We will examine here very briefly an account of two of the most significant currents of philosophic thought, stretching roughly from the 17th to the 18th Century surrounding the disputes between the Rationalists mainly from continental Europe, and the Empiricists of Britain. As forerunners to this period, it is useful to consider Francis Bacon and Galileo Galilei for their groundbreaking work in developing the scientific method during the scientific revolution. We will here be sticking to summarising the epistemology and metaphysics of these thinkers, and will focus on ethics, political philosophy and so on, in greater detail elsewhere.


Rene Descartes 1596-1650:
Granted as the Father of Modern Philosophy, Descartes’ work is the aptest and most traditional place to begin an account of Modern Philosophy. Responsible for relating a mathematical method to an understanding of reality in the sense that we are familiar with today. His pioneering work in geometric algebra would become critical in the development of mathematics, allowing us to plot the discoveries of Galileo and Kepler on a graph, his belief in the importance of mathematical understanding would go to inform what was to be one of the most significant ideological currents of the Enlightenment, Rationalism.

The medieval period of Philosophy had not moved significantly far from the principles set down Aristotle, and the education of Descartes would have been steeped in Aristotelian ideas, much of the it centered around logic. It is partly for this reason that Descartes was a revolutionary. Not content with continuing tradition, he wanted to begin afresh, by setting down a new foundation from which all knowledge and certainty could spring.

The importance of mathematical advancement is perhaps the most significant contributory factor in opening the door to this new conception of reality, humankind, and knowledge. By the end of the Renaissance, for the first time, texts including Algebra were produced and published, the artistic style of Realism was beginning to take shape, artists and writers studied mathematics to inform their works. When Man was making leaps in his conquest over nature. Mastery of agriculture, of the seas, with ambition for more, and with it came a certain confidence, encapsulated in the Rationalist project and its faith in our ability to comprehend reality; mechanistically, via reason / rationality, inherent in both the nature of: reality, and of ourselves, as the thinking things. And it was in this turn away from an Aristotelian faith in our senses to inform us where Descartes commences.

Descartes incorporates at the very beginning, a prerequisite to his writings, an absolute doubt toward Epistemology (knowledge), and thus of our ability to discern a Metaphysics from our knowledge. Descartes calls into doubt everything he knows to commence his meditations. Considering that his idea of God could be wrong, that God could, in fact, be a deceiver. All of the beliefs he holds, every sensation he has, could be nothing but an illusion caused by this God. Perhaps even the existence of his body, and his thoughts as he conceives of them are nothing but trickery; he asks then given this possibility of a false God, or demon, how is it that we may come to any knowledge of anything at all? This doubt gives way to what would be one of the most powerful notions in the history of Philosophy, known as the ‘Cogito’.

After much discussion on the possibility of such doubt, Descartes asserts that whether or not he has been tricked, there is one certainty he can attain to, that ‘I think’. Whatever it is thought, a delusion or not, and whatever the I, the subject ‘I’ posits itself, as proof of the existence of the something which is doing the thinking, thus ‘cogito ergo sum’, I think therefore I am. And so Descartes may commence from this first established certainty, an axiom of reason, that he exists with certainty, whether or not he may trust anything else remaining to be explored.

From this foundation, Descartes goes on to deduce that the essence of the I that thinks is that it is a thinking thing, and from this epistemological base he continues to unravel the existence and nature of God.

He discusses a piece of wax in its size, shape, colour, weight, and smell, and considers how it is that we recognise the same piece of wax after having melted it. The differently coloured, odourless mess on the floor, evades the senses to which empiricists give their faith, and so he learns to do away with his senses and to ascend into his realm of pure reason.

Baruch De Spinoza 1632-1677:
Spinoza, named Prince of Philosophers, of whom Gilles Deleuze remarks: “one is either a Spinozist or not a philosopher at all”. As remarkable, as he was rebellious – an undeniable genius. Like Descartes, the thought of Spinoza belongs to the tradition of reason, and is subject to the same presuppositions regarding our ability to describe mechanically reality, and by reason, come to an ultimate awareness of the divine and ourselves. Much like Descartes, the work of Spinoza flows from a man of true religiosity. Unlike the work of Descartes, though, we find in Spinoza’s magnum opus The Ethics an entirely new conception of God, it’s relation to reality, and man, culminating in what is one of the most comprehensive systems of thought in history.

Spinoza constructs his system in Ethics according to the geometric structure of Euclid’s Elements, which has formed the basis for most early mathematical teaching since publication around 300 BC, and for around 2000 years served as a textbook for Math and Geometry students. Beginning with definitions of the key concepts he will be using, Spinoza moves to build an axiomatic structure in which propositions and their proofs move upward from the basic, to the complex, via postulates, lemmas, and their corollaries to reach logical proofs. And it is in this sense firstly that we call the work Rationalist. A brief outline of the key conclusions will serve as a demonstration of the results he yields in attaining knowledge through the methodology of Reason in Ethics.

Ethics Part One: Concerning God. As mentioned, Spinoza transforms our traditional concept of God. Hitherto to the work of Descartes, there is essentially a separation of the finite and the infinite. There is God in his transcendental domain, and quite separately exists the reality of the finite; this including the two (again) separate realms of the mental/thought, and extension/materiality. To Spinoza though this will not do in defining God.

What is perceived clearly and distinctly and understood as God is the infinite. It is nothing less to Spinoza than a fact of the infinite that it is absolute, inclusive of everything, that which nothing can exist outside of, for otherwise infinity, it would seem, would be missing our reality from it, and we would have to admit an infinity plus.

The God of Spinoza is impersonal, and equates to the singular unified substance which underlies and constitutes all reality, substance here translating not to matter but “that which stands beneath”, this substance Spinoza refers to as, “Deus Sive Natura”, God or Nature. This substance, claims Spinoza, is an infinity of attributes, of which thought and extension are the only two graspable by humans, and which are actually the same things, expressed differently. Each attribute has modes of itself; these being examples of itself, and the modes can be infinite, or finite (these equating roughly to universals and particulars). As an example humankind might be seen as an infinite mode or expression of God’s attributes thought and extension, and I would be one finite mode of human-kind (though Spinoza denies the existence of universals or forms i.e. humankind, other than as formal essences in the intellect of God).

The first definition of the second book of Ethics, On the Nature and Origin of the Mind is revelatory in understanding the context of the life of an individual in Spinoza’s metaphysics:

DEFINITION I. By body I mean a mode which expresses in a certain determinate manner the essence of God, in so far as he is considered as an extended thing. (See Pt. i., Prop. xxv., Corolla.)

So that in the infinite and eternal unfolding of physical nature, each physical body is an expression of extension (the attribute), as a single finite mode. From our perspective today, it is as if God/Nature, much like a human, has both a body, and thoughts, and that every thought ever had by individuals are all ideas which make up the totality of thoughts of God / Nature. A neuron firing in a brain is also the same neuron triggering in the wider context of the universe, and each body of a human is relative to a skin cell or anything transient in God, temporary expressions of something permanent and eternal.

Spinoza devotes Book II to solving the mind-body problem as posited by Descartes, and as mentioned the resolution of Spinoza is that the order of ideas (thoughts) follow the order and connection of things (matter/extension). In other words, the very same causal relationship found in nature for physical objects equates to another string of ideal or psychic events which connect all of the ideas in reality. Ideas cannot cause anything physical, just as physical bodies cannot cause anything mental, rather they are two different expressions of one substance, and one nature.

At this point in the second book of Ethics, Spinoza encounters a problem in relation to our thoughts and the thoughts of God, for which he has an ingenious solution. The problem is that if God’s ideas are nothing but the entirety of ideas in Nature, then how can it be that false ideas are produced in God? or otherwise, if our ideas are the ideas of God, how is it that we may be fallible? Spinoza responds that whilst humans are capable of both adequate ideas (those which apprehend God’s absolute nature, and our relation to it), we are also prone to have inadequate ideas, false in us though only in God insofar as they are incomplete. Since a single idea in the ‘mind’ of God may exist in a person, it is necessary that in the wider connection of thoughts, the idea finds its completed sense, and thus apprehension of, if we like, metaphysics as Spinoza sees it.

Having clarified his perspective on the mind-body problem (dualism) Spinoza categorises the ideas the mind is capable of, as threefold. The first kind of knowledge is akin to induction, this being knowledge received via our senses or by use of arbitrary signs (i.e. language). Here we see intentional disregard for the empiricist project.

The second kind is that favoured by rationalism, i.e. knowledge attained by valid deductive reasoning such as the truths of mathematics and analytic statements like all men are mortal. The third kind, which we are to take as knowledge of the highest kind, is more abstract in nature, and is left somewhat vague, though explicable.

The third and most important type of knowledge is knowledge given by intuition, and which works as follows. The most simple explanation to give of intuitive knowledge is that it is a spontaneous, and momentary act of apprehension, like an epiphany, or realisation of the present, and which is eternally valid and applicable, and from which no further propositions follow by reason since it is in itself complete. It is a momentary awareness, acceptance, and bliss caused by the love of Nature or God’s completeness of which we are a part, it is to equate ourselves into the ever flowing chain of causality which is God’s perfect and determined nature. It must also be realised that as a dependent on God (or nature), as a mode of God, we give up our idea of free-will entirely, we are merely that which flows from God’s nature. Being dependent for our existence, and the nature of it, we are, as all of nature, entirely determined. Only God / Nature itself is self-determining since it follows only it’s own laws.

One final note before moving on is the significance of the ethical system which comes out of Ethics, since it is the title devoted to the text, and which relates spectacularly to his overall system. Good and Evil are not discussed in any absolute terms, and as with the rest of his system, they take a significant move away from traditional notions of morality, toward one of humanism. To Spinoza something is called good if and only if it is desirable to us, or:
“By good, I shall understand what we certainly know to be useful to us”
“By evil, however, I shall understand what we certainly know prevents us from being masters of some good”.

He goes on to explain that our ideas of “good” and “evil” are what we call things which cause us either joy or sorrow, and which relate in turn to our self-preservation.


John Locke 1632-1704:
Whereas the Rationalist accounts of epistemology grant reason as the spring of all knowledge, Locke – often referred to as the Father of Empiricism maintains Francis Bacon’s principle that all of our knowledge arises only through the faculty of our senses.

Locke commences the first book of his Essay Concerning Human Understanding by dismissing the ideas held by Descartes and later taken up by Leibniz. The ideas which he attacks cover those which claim that our knowledge is innate (a belief called innatism, which relates closely to nativism today), or a priori (arrived at independently of our senses, as with Descartes ‘Cogito’, or Spinoza’s grandiose system).

Locke’s disagreement with innatism argues that not even the most fundamental and principle kinds of knowledge which a Rationalist would take as innate such as that: A is A and not B, or that God exists, are viable. To Locke, these principles are little more than nonsense. He frequently turns to the example of developing children or idiots, to explain that things are not assented to universally. Locke explains that knowledge of complex ideas often takes many years of study to arrive at even a basic understanding. Thus, he concludes that the notion that ideas exist already in the mind is vacant if they are not in this sense immediate.

He also gives the example that many along with Descartes posit the existence of God as innate, yet many cultures either do not include conceptions of God, and those that do find no definite agreement in their conceptions. He makes the move to consider that we could, as explained, be in possession of certain innate ideas, and at the same time not be in possession of them. However, since for an idea to be in the mind for Locke, it is to be in conscious awareness, he is forced to conclude that A would be A and not A at the same time, thus violating one of the primary maxims of innate knowledge as held by the Rationalists.

Having begun his assault on innatism, Locke sets out how it is that we come to have ideas, in the second book of his Essay. The answer from Locke is simple, all ideas come from experience, and these can, and are to be divided into a series of sub-groups. We are born empty minded, a tabula rasa (blank sheet) in Locke’s words, to which.Firstly we have two kinds of experience, the first derived from our senses, and the second called reflection, a sort of introspection which includes doubting, thinking, and so on. Any single unit of perception, be it from our senses, or through reflection, is called a simple idea by Locke. The faculty of our mind to relate or compound these simple ideas, to put them together coherently, so that simple ideas combine the use of our senses toward the pen in hand, with our faculty to reflect on the function and so forth to call the complex and abstract idea of a pen.

Like Galileo, Locke distinguishes between primary and secondary qualities. Primary qualities as size, shape, number, and motion are to Locke things which are communicable from the object we apprehend, to our faculties themselves, and which are the things which we see as they are. On the other hand, secondary qualities are things like colour, odour, taste, or smell and which are things not found in objects, but which are mere ‘qualities’ that objects have the power to produce in us.

The fourth book of the Essay Concerning Human Understanding is where Locke finally arrives from his theory of ideas to his theory of knowledge. Perhaps the most important consideration here to bear in mind with Locke is that our knowledge pertains only to the connection of ideas, and not actually to the things in the world/reality outside of our minds. To Locke as far as the world external to our experience is concerned, we may have opinions or beliefs, absolute knowledge though is beyond our grasp, but for when we speak of ideas themselves.

Like Descartes and Spinoza, Locke designates three types of knowledge. The structure and order of the types of knowledge also look very similar to those established by his Rationalist opponents. The highest order is intuitive knowledge, as the kind of knowledge by which we need not apply any reasoning to but which alone stands as self-justifying, as an example of intuitive knowledge he gives our understanding of our existence, or of analytic propositions such as 1+1=2 or that white is not black. The second type of knowledge is that which follows demonstration so that demonstrative knowledge is that which must come about by connections of ideas, and which he gives the existence of God as an example. The third and most tenuous type of knowledge Locke calls Sensitive knowledge and is not granted the same status as knowledge as the prior two forms. Sensitive knowledge is more alike the highest possible probability than certain knowledge, and arises from the skepticism asks, if we only directly know our ideas, then how do we grant certainty at all to the world around us?

This problem is close to the skepticism Descartes employs to start his epistemological project. However rather than offering an account which supersedes experience (i.e. reason), Locke takes a variety of approaches to explaining that while we cannot have proof of the world outside of us; we have enough good reason to trust that it is as we experience it. If we are in error, we will remain so, so that in any case it would be better to disregard our distrust to a footnote of our thoughts.

David Hume 1711-1776:

The introduction of Hume’s Treatise of Human Nature sets out what for him is the foundation of all knowledge, typical of all of our epistemological philosophers here, in establishing a groundwork for what and how we can know things. Utterly opposed to rationalist accounts of innatism as we shall see, Hume follows Locke in finding our sensory perception to be the gate through which everything we know must pass. For Locke a tabula rasa is our starting point for acquiring knowledge, Hume though identifies what makes possible even this blank page to conclude that all knowledge, including those types found in science and mathematics, to be ultimately rooted in a science of man, that is – in our psychology. If this seems confusing, understand that to Hume our knowledge of things depends upon our human faculties, starting with our senses, and so what we call knowledge is more to do with how we as a human understand, than it is about an understanding of reality itself.

Hume begins his treatise, as Locke in his essay on human understanding, by considering the origin and nature of our ideas. Here Hume lays out an archetypal empirical groundwork in concluding that all possible knowledge and ideas are made up of little impressions which make up the totality of our perception.

Impressions are what we receive through our senses and our internal feelings, and Ideas are linked as their inward reflection so that all of our ideas are formulated by parts known first to us as simple sense impressions, this idea is known as Hume’s copy thesis. He defines simple impressions as those isolated such as perceiving a: colour, size, shape, movement, and so on including primary and secondary qualities. The other basic type of perception he names complex, and which is merely the compounding, or other relation to more than one simple impression i.e. when we conceive of an apple as a combination of the simple impressions: small, round, green, and so on.

In distinguishing ideas from the impressions they copy, Hume argues that the only difference is the liveliness and vivacity with which impressions strike compared with their copies (in ideas). It has been pointed out that since in Hume’s account ideas and the mental are essentially corporeal functions, which he is here giving an early physicalist theory of the mind by not distinguishing strongly between the impressions of our body and the ideas they entail.

Hume distinguishes impressions of two kinds, those met through our sensory faculties as explained, and which are external, and from reflection and thus internal and which is involved with the emotions, he then sets impressions aside to deal further with our ideas.

So as we’ve said, to Hume, our ideas are always composed of data collected by us through sensory impressions. He divides ideas into those in the memory – which retains the order and structure of the impression from which they originate, and the imagination – which though weaker in forcefulness than memory, can re-arrange sensory datum to invent things which do not necessarily have a correspondent in reality. Hume considers our creative, imaginative faculty to be capable of four principal operations in which it re-arranges sense data, these being: compounding, transposing, augmenting, and diminishing.

Compounding is simply the addition of things together to create a new thing, as when I add my idea of the sky, and the colour of gold to conceive of a golden sky. Transposition as when substituting the component of one thing for one from another, as a man with ears for eyes, and eyes for ears. Augmentation as when we imagine something greater in scale or number than we can perceive, like imagining the universe, or imagining a giant man. Finally, diminishing, as the opposite to augmentation.

While our imagination is to Hume more free and creative than our other faculties it is still subject to certain psychological tendencies which are defined by resemblance, contiguity, and causation. He also orders seven relations which the imagination is capable, and he divides the relations which he later calls: associations of ideas, or, matters of fact. Moreover, here we encounter one of the most crucial features of Hume’s epistemology.

The division of associations of ideas and matters of fact is the division between, what on one hand we may certainly know to be true, and on the other that which we can only have confidence and faith in. These things help us to navigate the world sanely, but for Hume will remain always uncertain, and thus does not qualify as knowledge, but only probable knowledge.

The division is known as Hume’s fork, and it is, on the one hand, relations/associations of ideas and which describes the operations of our reason, and which corresponds with what we may have certain knowledge of. It is thus always: necessary; analytic (true by the definitions of the terms employed; as 2+2=4 or I = Man, Man = Mortal, thus I = Mortal), and a priori insofar as it does not require any experimentation for proof but is immediately clear as an impression. On the other side, we have the knowledge of which Hume is famously skeptical, knowledge of matters of fact, that is knowledge of the reality we exist in and as a part. The knowledge we have of matters of fact is opposed to that of ideas, defined instead as contingent, synthetic, and a posteriori. The problem here is known as the problem of induction, and it has plagued humanity’s thought for millennia and which persists today.

Hume has a problem in comprehending how it is that our faculties allow for an understanding of matters of fact. According to Hume’s seven relations which our imagination is capable of, all seem to be knowable to us with the use of our senses apart from one – causality. Causality clearly cannot be perceived deductively i.e. via reason, since he says of a given cause we can, by reason conceive of a variety of effects which might follow. He considers rolling a billiard ball at another, that we might reasonably predict one to knock the other and for both to continue rolling, or the first to halt while the second bounces off, they could both be caused to stop, or the ball could even be conceived to jump over the second and continue. Rather we must find our knowledge of this type of thing, of the subjects of science, regarding the world around us, by induction and faith in experimentation. So we record the behaviour of the ball and its motion and relation to the other ball until a sufficient amount of data is gathered to make judgements and rules regarding the motion of the balls. From this point, we continue to assume that the rules will hold in the future as they have been recorded in the past. This for Hume is the irreconcilable problem of induction; it is the assumption that “the sun will rise tomorrow” simply since it always has, does not for Hume satisfy certain knowledge. This problem as highlighted by Hume was received with drastic results, including to shake the foundation of the way we were beginning to see the universe, including the work of Isaac Newton.

Without reading directly from the works of Hume, a summary of the extremely dense ideas he outlines over many a lengthy Treatise or Enquiry may seem to be petty in their conclusions. However, bear in mind that we have only really considered the epistemology and a little of the metaphysics of the philosophers written of here. Their works could equally have been regarded from the view of their philosophy of Ethics, Language, Religion, Psychology and so on.

To Conclude

The division between rationalism and empiricism is often treated as a very severe one though we can clearly draw many similarities between the two movements. I suppose the clearest separation in ideology between thinkers in the British tradition, and their contemporaries across Europe is that rationalists believe that our minds are in some sense pre-figured with knowledge, and which to attain we need only follow the faculty of reason. To the empiricist, though we come into the world devoid of anything, even the capacity for learning is learned, and at the root of all lies our basic sensory faculties. We notice in the first group a distinct faith in our ability to attain ambitious types of knowledge, and in the second, one far more skeptical about these claims.

To the rationalist, empiricism fails for a few key reasons, it seems difficult to conceive of an ethical philosophy derived from experience, for example, and it also seems difficult to derive the truths of math and logic from experience, despite the empiricists proclamation that we can. Rationalists object to many other consequences following from empiricism, it seemingly limits our capacities and understanding somewhat significantly, and finally that the experimental, observational methods of epistemology seem unable to test whether or not their sensory observations correspond with reality is problematic.

The problem in return for empiricists is that it seems nonsensical to suppose ourselves to be in possession of innate knowledge which we do not have an awareness of, even the possibility seems empty since we need to come to that reasoning through the experience of the world anyway. If we consider someone born blind, no explanations or descriptions of colours, shapes, bodies in motion and so on would have much utility. Reason as a primary source of knowledge takes a complicated twist given the lack of experience for the blind person in conceiving the descriptions. No matter what reasoning we give we still seem unable to account for the missing essentiality of experience. How can reason reveal what is immediately evident to the senses?

Both however are focussed on epistemology and engage in mutual dialogue with one another; both are also involved with advancing science (rationalists primarily with mathematics/geometry/logic, empiricists with the natural sciences and the experimental method), and both struggle around the issue of how the mind and body cooperate.
The two streams of thought converge in the work of Immanuel Kant and his philosophy of transcendental idealism which seeks to reconcile rationalism and empiricism in his Critique of Pure Reason.

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