The memory, senses, and understanding are, therefore, all of them founded on the imagination, or the vivacity of our ideas.
No wonder a principle so inconstant and fallacious should lead us into errors, when implicitly followed (as it must be) in all its variations.
It is this principle, which makes us reason from causes and effects; and it is the same principle, which convinces us of the continued existence of external objects, when absent from the senses.

But though these two operations be equally natural and necessary in the human mind, yet in some circumstances they are [Sect.

4.] directly contrary, nor is it possible for us to reason justly and regularly from causes and effects, and at the same time believe the continued existence of matter.

How then shall we adjust those principles together?
Which of them shall we prefer?
Or in case we prefer neither of them, but successively assent to both, as is usual among philosophers, with what confidence can we afterwards usurp that glorious title, when we thus knowingly embrace a manifest contradiction?
This contradiction [Part III.Sect.

14.] would be more excusable, were it compensated by any degree of solidity and satisfaction in the other parts of our reasoning.