Lockean vs Cartesian Epistemology

Photo by Elisa Calvet B. on Unsplash

Anyone who has taken a psychology class is likely familiar with the Nature vs Nurture debate. That is, the debate over the extent to which our innate human nature or upbringing affect our behaviour and identity. What many might not know, however, is that this debate goes as far back as the 17th century and has its roots in philosophy. Two of the most influential philosophers in this debate were French rationalist philosopher René Descartes and English empiricist philosopher John Locke. Between the two of them, we will examine who has a more accurate understanding of the human person and how we acquire knowledge.

John Locke was an English philosopher of the 17th century into the early 18th century. While he is primarily known for his philosophy, he initially started his professional career as a medical doctor and began writing philosophical works later in life. Locke’s background in science might have something to do with his allegiance to the Empiricist philosophical tradition. Locke is perhaps better known for his political philosophy, but his writings on epistemology (i.e., what we can know and how we know it) have been deeply influential since their publication. Locke’s rejection of innate ideas, for example, and suggestion that the human is a tabula rasa, (Latin for blank slate), to be shaped by experience, has taken root in many other philosophies associated with the political left (e.g., those of Karl Marx, Simone de Beauvoir, etc.). In his An Essay Concerning Human Understanding Locke, despite his faults, does indeed make a strong case for his philosophy and brings interesting challenges to Rationalists.

Before comparing Locke and Descartes, however, let us first sketch out a basic understanding of both philosophies. As previously mentioned, Locke’s ideas were primarily grounded in empiricism, which is to say that ideas are primarily derived from one’s experience of the world, i.e., sensation and reflection. On the other hand, subscribers to Rationalism, such as René Descartes, believed that since we are so often led astray by our senses, it is necessary to primarily use reason as a foundation for acquiring knowledge;

“…I have noticed that the senses are sometimes deceptive; and it is a mark of prudence to never place our complete trust in those who have deceived us even once.”

-René Descartes, Meditations on First Philosophy

So how are ideas and knowledge acquired? From experiencing things with similar characteristics, Locke believed, one would be able abstract all of the differences between them and create an idea of that common characteristic. For example, one may observe both a blue bird and a blueberry and abstract the idea of "blueness". These immediately perceivable ideas, such as extension, colour and taste, for example, Locke referred to aptly as simple ideas. Complex ideas or mixed modes are combinations of simple ideas. Since ideas are primarily derived from the senses, according to Locke, it logically follows that no human could possibly have any innate ideas. Like Descartes, however, Locke believed that an idea on its own has no innate truth or falsehood, rather it is a judgement of agreement or disagreement between ideas that has truth or falsehood. Recognising this agreement or disagreement between ideas (e.g., a blueberry is blue, or a horse is not a turtle) is what Locke considers to be knowledge.

Because Locke believes that humans obtain ideas from experience, and thus substance, this brings us to an interesting question; what, metaphysically speaking, is substance? Humans do indeed obtain ideas from these things, but how do these ideas make the leap from abstract to tangible? Locke proposes the idea that substance is what ties all of these properties together to create an object; a sort of fundamental substratum. The substances themselves do not hold ideas of properties, these ideas are, rather, created in our minds. Locke also admits that we are unable to directly have experience of pure substance as we are only ever able to experience any given object through its properties.

“[I]f anyone will examine himself concerning his notion of pure substance in general, he will find that he has no other idea of it at all, but only a supposition of he knows not what support such qualities, which are capable of producing simple ideas in us…”

-John Locke, An Essay Concerning Human Understanding

This is an interesting metaphysical claim by Locke as it seems to directly contradict his epistemology as it is not an empirically verifiable claim. For if we cannot experience pure substance, how do we know that it is there? Indeed one can infer that it is necessary to tie abstract qualities together into matter, but it also becomes a weakness in Locke’s philosophy that is exploited by later idealists, or those that believe that matter does not exist, only ideas.

If we are to believe that knowledge is derived primarily through the senses one must ask, how is it that we can have knowledge of things that we do not directly experience? One might propose the solution that one may simply ask another who was actually there, but this only pushes the question back further because he or she still does not have experience of something else which he or she does not directly experience. Empiricism also seems to be insufficient to answer how one comes to understand certain concepts, like that of infinity. Locke seems to believe that an understanding of infinity is reached through the continuous addition of any given unit to itself; such as with abstract numbers or physical space.

“Finite, and infinite, seem to me to be looked upon by the mind, as the modes of quantity, and to be attributed primarily in their first designation only to those things, which have parts, and are capable of increase or diminution, by the addition or subtraction of any the least part: and as such are the ideas of space, duration and number…”

-John Locke, An Essay Concerning Human Understanding

Some philosophers, such as Georg Hegel, refer to this as “bad infinity” as this way of understanding infinity itself implies a sort of finitude to some degree because any addition to, or subtraction from, infinity would still be infinity (as opposed to “infinity”± n). This differs from René Descartes idea of infinity in a fundamental way. First, Descartes believes that infinity is simply that without limit and is understood specifically not by negating finitude. Second, Descartes believes that one cannot produce the idea of infinity on one’s own and must be understood a priori i.e., independent of experience. His reasoning for this is because one cannot have any direct experience of anything infinite since all things in the universe, including humans, are finite beings, thus it is necessary that this idea of infinity be innate and originating from its infinite source (i.e., God). Locke’s epistemology seems to translate to a lack of clarity on the nature of God, for while Locke concedes that God cannot be fully understood, God is less easily understood, or even misunderstood, by his account. This is because Locke’s idea of infinity is conceived from quantifiable things from which units can be subtracted or added, but how does this apply to more abstract, non-quantifiable modes such as wisdom, power, goodness, etc.?

On the other hand, Empiricism seems to fill in some intellectual gaps left by the Rationalist epistemology. Indeed, things may come to be known in a vacuum such as mathematical proofs, but what about logical deduction from a set premises that require knowledge about the world? It seems that the data to inform these premises would have to be derived from experience. Reason is indeed a powerful tool, but it cannot be applied to the real world in a meaningful way without prior experience to inform or cultivate said reason. One must ask also, how can ideas be innate, and if they do exist, which ones? Of innate ideas, Locke says,

“Not naturally imprinted, because… ’tis evident that all children and idiots have not the least apprehension or thought of them… For to imprint anything on the mind without the mind’s perceiving it, seems hardly intelligible.”

-John Locke, An Essay Concerning Human Understanding

If infants or children, who lack experience of the world, demonstrate no knowledge of any innate idea, it must follow that they likely do not exist. Locke then goes on to say that if one forms innate ideas through coming to reason, then it follows that they cannot be innate precisely because coming to know them is contingent upon cultivating the ability to reason. Like Descartes, Locke believes that God can be known with certainty, though he disagrees that God is known innately. For example, if God were an innate idea, why is it that different individuals and groups have different conceptions of what God is? Additionally, children do not seem to be aware of God innately, as knowledge of God requires demonstration.

It seems as though John Locke’s epistemology can raise questions that may be difficult for its counterpart to answer. Rationalism, however, seems to hold up to more scrutiny. While both are imperfect, comparing the two can help one come to a more clear and truer picture of what we know and how we know it. Indeed, due to our imperfect nature, there shall always be questions.



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