Imagination is the recollection of certain impressions. But it seems necessary to believe that there is a difference between the recollection of certain impressions and the actual experience of certain impressions. But as such, would reducing self-identity to the experience of impressions (being what I infer to be meant by the 'stream of impressions') not be to undercut the way in which we can provide a basis for the possibility of imagination? Furthermore, what allows for associations, being generally the considerations of similarities and differences between impressions, if not intentional functions of a self-identity that is itself able to carry out such associations only because it is not itself reducible to the impressions in question? To clarify, Hume considers associations to be organizations of impressions. Hume's three associations, being resemblance, contiguity, and cause and effect, are all thus thoughts about impressions experienced. But as such, how can such thoughts possibly be said to be a part of the very 'stream' of experienced impressions, or reducible to impressions, if in fact such thoughts involve the capacity to recall and analyze impressions not actually currently experienced? More primarily, how can our organizational capacities be said to be reducible to that which is organized?
David Hume deals with the question in Book 1 of his work “A Treatise of Human Nature”. The content of our consciousness are either
- Impressions: Typical impressions are our sensations, passions and emotions. They are characterized by their intensity.
- Or ideas. The faint image of impressions are ideas created by our thinking and reasoning.
Hume uses the term perception as generic term covering both impression and idea.
Hume identifies three properties of ideas inducing the mind to link simple ideas to associations, namely
- contiguity, meaning that two ideas refer to neighbourhoud in time and space,
- and cause and effect.
I interpret your first questions after the clarification as follows: How can ideas be reduced to impressions, when the latter formed part of the stream of consciousness and have passed long ago?
In Book 1, part VI, chapter 6, Hume speaks about the fundamental role of the memory, e.g. to create the idea of an identical object:
In this particular, then, the memory not only discovers the identity, but also contributes to its production, by producing the relation of resemblance among the perceptions.
I conclude that according to Hume, the memory stores simple impressions as simple ideas. Hence these ideas become persistent.
Unfortunately, your second question after the clarification is still unclear to me: Which organizational capacities do you mean? Why are they reducible according to Hume?