Book 1, Part 4, On the Sceptical and Other Systems of Philosophy Summary and Analysis

1.4 discusses skepticism about various common sense features of reality. His theory of perception will show that even the apparent endurance of objects over time, INCLUDING THE SELF, are mere perceptions and have no reality. Reason and the senses give no knowledge on these matters, while the senses and automatic inference do not produce these ideas, only the imagination, which is often unreliable. We never experience objects persisting through time, only our successive perceptions of them. And we never experience ourselves directly either. Impressions cannot produce these ideas.

Hume thinks it is pointless to wonder about the existence of the external world and external objects. We should just presume that it is true, although it is fruitful to ask what it is about human...