At first our pupil had merely sensations, now he has ideas; he could only feel, now he reasons. For from the comparison of many successive or simultaneous sensations and the judgment arrived at with regard to them, there springs a sort of mixed or complex sensation which I call an idea. The way in which ideas are formed gives a character to the human mind. The mind which derives its ideas from real relations is thorough; the mind which relies on apparent relations is superficial. He who sees relations as they are has an exact mind; he who fails to estimate them aright has an inaccurate mind; he who concocts imaginary relations, which have no real existence, is a madman; he who does not perceive any relation at all is an imbecile. Clever men are distinguished from others by their greater or less aptitude for the comparison of ideas and the discovery of relations between them. Simple ideas consist merely of sensations compared one with another. Simple sensations involve judgments, as do the complex sensations which I call simple ideas. In the sensation the judgment is purely passive; it affirms that I feel what I feel. In the percept or idea the judgment is active; it connects, compares, it discriminates between relations not perceived by the senses. That is the whole difference; but it is a great difference. Nature never deceives us; we deceive ourselves.

. . . These two are the fountains of knowledge, from whence all the ideas we have, or can naturally have, do spring.

3. The objects of sensation one source of ideas. First, our Senses, conversant about particular sensible objects, do convey into the mind several distinct perceptions of things, according to those various ways wherein those objects do affect them. And thus we come by those ideas we have of yellow, white, heat, cold, soft, hard, bitter, sweet, and all those which we call sensible qualities; which when I say the senses convey into the mind, I mean, they from external objects convey into the mind what produces there those perceptions. This great source of most of the ideas we have, depending wholly upon our senses, and derived by them to the understanding, I call SENSATION.

4. The operations of our minds, the other source of them. Secondly, the other fountain from which experience furnisheth the understanding with ideas is,- the perception of the operations of our own mind within us, as it is employed about the ideas it has got;- which operations, when the soul comes to reflect on and consider, do furnish the understanding with another set of ideas, which could not be had from things without. And such are perception, thinking, doubting, believing, reasoning, knowing, willing, and all the different actings of our own minds;- which we being conscious of, and observing in ourselves, do from these receive into our understandings as distinct ideas as we do from bodies affecting our senses. This source of ideas every man has wholly in himself; and though it be not sense, as having nothing to do with external objects, yet it is very like it, and might properly enough be called internal sense. But as I call the other SENSATION, so I Call this REFLECTION, the ideas it affords being such only as the mind gets by reflecting on its own operations within itself. By reflection then, in the following part of this discourse, I would be understood to mean, that notice

Most of the ideas which are capable of making a powerful impression on the mind, whether simply of pain or pleasure, or of the modifications of those, may be reduced very nearly to these two heads, self-preservation, and society.

The acts of the mind, wherein it exerts its power over simple ideas, are chiefly these three: 1. Combining several simple ideas into one compound one, and thus all complex ideas are made. 2. The second is bringing two ideas, whether simple or complex, together, and setting them by one another so as to take a view of them at once, without uniting them into one, by which it gets all its ideas of relations. 3. The third is separating them from all other ideas that accompany them in their real existence: this is called abstraction, and thus all its general ideas are made.

All our Ideas, or the materials of our reasoning or judging, are received by some immediate Powers of Perception internal or external, which we may call Senses … Reasoning or Intellect seems to raise no new Species of Ideas, but to discover or discern the Relations of those received.

Idea or Vision, in its sensuous meaning, would be something that could be perceived only by the bodily eye and not by any other sense such as taste, hearing, etc.; it would be such a thing as a rainbow, or the forms which pass before us in dreams. Idea or Vision, in its supersensuous meaning, would denote, first of all, in conformity with the sphere in which the word is to be valid, something that cannot be perceived by the body at all, but only by the mind; and then, something that cannot, as many other things can, be perceived by the dim feeling of the mind, but only by the eye of the mind, by clear perception.

It is a remark which needs no subtle reflection to make, but which we may assume that even the commonest understanding can make, although it be after its fashion by an obscure discernment of judgment which it calls feeling, that all the 'ideas' that come to us involuntarily (as those of the senses) do not enable us to know objects otherwise than as they affect us; so that what they may be in themselves remains unknown to us, and consequently that as regards 'ideas' of this kind even with the closest attention and clearness that the understanding can apply to them, we can by them only attain to the knowledge of appearances, never to that of things in themselves.

Thus we see, that the mind can undergo many changes, and can pass sometimes to a state of greater perfection, sometimes to a state of lesser perfection. These passive states of transition explain to us the emotions of pleasure and pain. By pleasure therefore in the following propositions I shall signify a passive state wherein the mind passes to a greater perfection. By pain I shall signify a passive state wherein the mind passes to a lesser perfection. Further, the emotion of pleasure in reference to the body and mind together I shall call stimulation (titillatio) or merriment (hilaritas), the emotion of pain in the same relation I shall call suffering or melancholy. But we must bear in mind, that stimulation and suffering are attributed to man, when one part of his nature is more affected than the rest, merriment and melancholy, when all parts are alike affected. What I mean by desire I have explained in the note to Prop. ix. of this part; beyond these three I recognize no other primary emotion; I will show as I proceed, that all other emotions arise from these three.

I believe that this notion of our having a simple pain in the reality, yet a delight in the representation, arises from hence, that we do not sufficiently distinguish what we would by no means choose to do, from what we should be eager enough to see if it was once done. We delight in seeing things, which so far from doing, our heartiest wishes would be to see redressed.

Thoughts are strange things. they have 'representational' powers: a thought typically represents the world as being one way or another. A sensation, by contrast, seems to just sit there.

Ideas are refined and multiplied in the commerce of minds. In their splendor, images effect a very simple communion of souls.

The better to understand the nature, manner, and extent of our knowledge, one thing is carefully to be observed concerning the ideas we have; and that is, that some of them are simple and some complex.

If we take an unprejudiced view of the processes of consciousness, free from all the so-called association rules and theories, we see at once that an idea is no more an even relatively constant thing than is a feeling or emotion or volitional process. There exist only changing and transient ideational processes ; there are no permanent ideas that return again and disappear again.

On the whole, it appears to me, that what is called taste, in its most general acceptation, is not a simple idea, but is partly made up of a perception of the primary pleasures of sense, of the secondary pleasures of the imagination, and of the conclusions of the reasoning faculty, concerning the various relations of these, and concerning the human passions, manners, and actions.