So far, we have discovered that Hume is intending to employ an empirically based and reasoned approach to his investigation of human nature, or "the ultimate principles of the soul". Hume recognises at the outset that this is not going to be easy. Many others have set out on the same road, only to realise the impossibility the task. Indeed, it may be more prudent not to attempt such an enquiry, and thereby "avoid falling into error"; but we clearly get the impression by this point that Hume is quite willing to give it a try, or even perhaps believes that he has solved the problem.
It seems evident to Hume that we cannot "go beyond experience, or establish any principles that are not founded on that authority" (i.e. experience). Here we have a clear statement of empiricism. It will be interesting to see why Hume thinks this is self evident, and what conclusions he draws even allowing for such limitations.
Book 1 - Of the Understanding
In Section 1 - Of the Origin of our Ideas, Hume begins to lay the groundwork and first draws a key distinction between two different types of perception: impressions and ideas. The difference between these two types of perception is "the degree of force or liveliness with which they strike upon the mind, and make their way into our thought or consciousness."
It is interesting to me that, by starting at this point in his first book on philosophy, Hume has already taken quite a lot for granted. Unlike Descartes in Discourse on the Method, Hume hasn't questioned the concept of self or indeed of perception. It seems to be taken for granted that there is someone who perceives and something being perceived.
Further, we may need to go on to investigate if this distinction between impressions and ideas is the same, or similar, to philosophical dualism; for example, the Cartesian dualism between essence and existence which can be seen in Descartes' writings.
For Hume, impressions are the more vigorous type of perception, and include sensations, passions and emotions. Ideas are described as "fainter images" of these and include thinking and reasoning.
Hume says "I believe it will not be very necessary to employ many words in explaining this distinction." I'm not sure I entirely agree that we can just accept this - a number of objections immediately spring to mind. For example, it is not always the case that emotions strike us more forcefully than reflective thoughts. Also, we have the case of dreams, where the distinction between Hume's impressions and ideas is much less clear-cut. For the time being however, I shall give Hume the benefit of the doubt and move on.
Hume then immediately recognises that the two counter-arguments above may be raised in objection, but concludes that it is nevertheless true that ideas and impressions are "in general so very different, that no-one can make a scruple to rank them under distinct heads".
Next, Hume draws a distinction between simple and complex perceptions (both ideas and impressions). "Simple perceptions ...are such as admit of no distinction or separation. The complex are the contrary to these." For example, the idea of an apple is complex as it comprises a number of components. The components of the idea of an apple such as smell, taste and colour are simple perceptions.
Again, I think we can see what Hume is getting at, but I'm not convinced that our perceptions can be so clearly categorised. Indeed, objections to this theory can be quite extreme, such as the "compositionally nihilist" view, which renounces the literal existence of complex perceptions*.
Hume does not recognise any other possible distinction between impressions and ideas other than the degree of force and vivacity by which they are perceived. He says the two are remarkably similar in all other respects, indeed many (simple) impressions are subsequently perceived as ideas when we reflect upon or recall them. This lack of flexibility is a little alarming, but just because it doesn't at first pass the "smell test" doesn't necessarily make it unhelpful, we shall see.
In Hume's defence, I think we can all recognise the difference between a 'sense perception' and a 'thought'. If this distinction proves to be useful in formulating a theory of human nature, we should probably give Hume some leeway before rejecting his conclusions as being based on dodgy foundations.
Hume claims next that every simple idea has a simple impression that resembles it and vice versa, but this is not necessarily true for complex ideas and complex impressions.
Hume's "general proposition" which will be more fully examined in the Treatise is stated as follows: "That all our simple ideas in their first appearance are deriv'd from simple impressions, which are correspondent to them, and which they exactly represent."
From this we take it that all simple ideas are preceded by (and later we find also caused by) a corresponding simple impression.
With regards to this proposition, Hume challenges us to come up with an exception to prove him wrong. I am slightly cheating here because I remember from my student days one exception which Hume examines next, namely the case of the missing shade of blue. If someone has seen lots of different shades of blue, but not one particular shade, it is argued that they could form an idea of this missing shade of blue, even if that they have not previously perceived that shade via a corresponding impression.**
Hume does not find this exception to be fatal, indeed he manages to convince himself that in a way it is the 'exception that proves the rule'. Ideas "produce the images of themselves" in new ideas, but "as the first ideas are supposed to be derived from impressions, it still remains true that all our simple ideas proceed either mediately or immediately, from their correspondent impressions". Hume believes therefore that his proposition still stands, because in the very rare case where a simple idea is not caused by a corresponding simple impression, that simple idea is in fact caused by copying another simple idea, which in turn was caused by a simple impression.
In the conclusion of section 1, Hume is confident that he has dispensed with any notion of innate ideas***.
I will continue with Section 2 tomorrow.
* See 'Hume on the Individuality of Complex Perceptions' by Jani Hakkarainen (2011) for an analysis of this issue.
See 'Hume’s Missing Shade of Blue Re-viewed' by John O. Nelson in Hume Studies Volume XV Number 2 (November 1989)
*** Innatism is a philosophical doctrine that holds that the mind is born with ideas/knowledge, and that therefore the mind is not a 'blank slate' at birth, as early empiricists such as John Locke claimed. It asserts therefore that not all knowledge is obtained from experience and the senses. (from Wikipedia)