| 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. |
| To hate, to love, to think, to feel, to see; all this is nothing but to perceive. |
| Now since nothing is ever present to the mind but perceptions, and since all ideas are derived from something antecedently present to the mind; it follows, that it is impossible for us so much as to conceive or form an idea of any thing specifically different. |
| from ideas and impressions. |
| Let us fix our attention out of ourselves as much as possible: Let us chase our imagination to the heavens, or to the utmost limits of the universe; we never really advance a step beyond ourselves, nor can conceive any kind of existence, but those perceptions, which have appeared in that narrow compass. |
| This is the universe of the imagination, nor have we any idea but what is there produced. |
| The farthest we can go towards a conception of external objects, when supposed SPECIFICALLY different from our perceptions, is to form a relative idea of them, without pretending to comprehend the related objects. |
| Generally speaking we do not suppose them specifically different; but only attribute to them different relations, connections and durations. |
| But of this more fully hereafter.[Part IV, SECT. 2.] |
| PART III. OF KNOWLEDGE AND PROBABILITY. |
| SECT. I. OF KNOWLEDGE. |
| There are seven [Part I. SECT. 5.] different kinds of philosophical relation, viz. |
| RESEMBLANCE, IDENTITY, RELATIONS OF TIME AND PLACE, PROPORTION IN QUANTITY OR NUMBER, DEGREES IN ANY QUALITY, CONTRARIETY and CAUSATION. |
| These relations may be divided into two classes; into such as depend entirely on the ideas, which we compare together, and such as may be changed without any change in the ideas. |
| It is from the idea of a triangle, that we discover the relation of equality, which its three angles bear to two right ones; and this relation is invariable, as long as our idea remains the same. |