Any idea we please to form is the idea of a being; and the idea of a being is any idea we please to form.
Whoever opposes this, must necessarily point out that distinct impression, from which the idea of entity is derived, and must prove, that this impression is inseparable from every perception we believe to be existent.

This we may without hesitation conclude to be impossible.
Our foregoing reasoning [Part I.Sect.

7.] concerning the distinction of ideas without any real difference will not here serve us in any stead.
That kind of distinction is founded on the different resemblances, which the same simple idea may have to several different ideas.

But no object can be presented resembling some object with respect to its existence, and different from others in the same particular; since every object, that is presented, must necessarily be existent.
A like reasoning will account for the idea of external existence.

We may observe, that it is universally allowed by philosophers, and is besides pretty obvious of itself, that nothing is ever really present with the mind but its perceptions or impressions and ideas, and that external objects become known to us only by those perceptions they occasion.