Hume and Kant

Hume and Kant (1700s)

David Hume

Scottish philosopher David Hume agreed with Berkeley's claim that we are not directly acquainted with any properties of the external world, but this did not lead him to accept idealism, the view that physical objects do not exist. Instead, he remained just as sceptical about the existence of the mind. In 1748, Hume combined Descartes' rationalism with Locke's empiricism and argued that we gain knowledge from both impressions, which correspond to Locke's sensations, and ideas, which are innate.

Hume argued that innate ideas, like those found in mathematics, do not tell us anything useful about the external world. All useful knowledge comes from the qualia we experience but this does not tell us anything that is necessarily true. Hume argued that qualia make little sense to us until our minds have learnt to interpret them and that interpretations occur by custom, instinct and habit; if we experience two events in succession enough times, then we will come to expect one event after witnessing the other.

Hume applied this reasoning to science and argued that we only assume the future will resemble the past, and that the laws of physics will not suddenly change, because this is how the world has always appeared to us. But our experience and understanding are limited; we could be in the same position as a farm animal who associates their owner with food and has no reason to think that they will one day hurt them.

Hume argued that knowledge of the self is also formed by custom and habit. He could not see any evidence that the mind is made of a non-physical substance or that it persists through time separately from the body. Hume described the mind as a "bundle" (Hume, pp.200) of qualia, and did not think there was any evidence of something that takes ownership of these sensations, a self. Although Hume accepted that there are thoughts, he did not accept Descartes claim that this means there is a thinker. In a similar fashion, Hume did not think that there was any evidence of God. Like Hobbes, he did not think that the mind could conceive of such an entity.

Immanuel Kant

German philosopher Immanuel Kant began as a rationalist but was inspired by the work of Hume and, in 1781, he also developed a theory which combined rationalism with empiricism. Kant argued that true knowledge could only be acquired by combining rationalist ideas with empirical knowledge. This is because he believed that rationalism becomes flawed when it tries to consider anything beyond our sensory experiences, including the existence of God, freewill and the idea of an immortal soul.

Before Kant, both empiricists and rationalists had accepted that rationalism could only explain analytic knowledge. Analytic knowledge derives from statements which are true by definition. Kant stated that "all bodies are extended" (Kant, pp.7) is an example of an analytic statement because being 'extended' in space is part of the definition of being a body. Other examples are 'all daisies are flowers' and 'all triangles have three sides', this is because being a flower is part of the definition of being a daisy and having three sides is part of the definition of being a triangle. These are contrasted with synthetic statements, statements which provide information about the world. Examples of synthetic statements include 'all daises are pretty' or 'all triangles are green'.

It was believed that synthetic knowledge could only be known from experience, however Kant argued that that this is false. Kant believed that mathematics is a kind of rationalist synthetic knowledge because, despite the fact that 7 + 5 = 12, for example, there is nothing within the + sign, or the numbers 7 or 5, which give the definition of 12. This means that our knowledge of mathematics comes from an innate knowledge of the external world. Kant extended this idea to the foundations of physical science and argued that another example of a rationalist synthetic statement is 'the shortest distance between two points is a straight line'. This is because the concept of a straight line is not part of the definition of 'the shortest distance between two points' (Kant, pp.10).

Kant argued that aside from rationalist synthetic knowledge, the only way to gain information is through analytic statements which are entirely empirical. But because we can only perceive of qualia, Kant accepted Hume's conclusion, that our capacity for thought is too limited to conceive of objects as they really are and purely empirical knowledge is formed only by custom, instinct and habit.

Kant argued that the mind is needed in order to make sense of the continuous stream of qualia that we perceive. He claimed that external objects exist outside of time and space and the mind is needed to organise qualia into separate spatial and temporal locations. This means that the concepts of space and time are rationalist in nature, they are not learnt from experience. The mind is also needed to join associated qualia into the objects we recognise. In order to do this, Kant agreed with Descartes when he stated that the mind must necessarily be a unified whole. Kant did not accept dualism however, because the idea of an immortal soul is also formed by custom, instinct and habit.

Kant stated that the mind is really just a complex set of abilities, or functions, without a subject; "the permanence of the soul, therefore, as an object of the internal sense, remains undemonstrated, nay, even indemonstrable." We cannot "affirm, from mere conceptions" the souls "permanence beyond life" (Kant, pp.246).

References

Hume, D., 2004, 'Enquiry concerning Human Understanding', Barnes & Noble, NewYork

Kant, I., 1855, 'Critique of Pure Reason', Miller Dow Meiklejohn, J., (trans.), Henry G. Bohn, London