18. Further, man is endued with a sort of creative power: he can fabricate images of things that have no existence. The materials employ’d in this operation, are ideas of sight, which may be taken to pieces and combined into new forms at pleasure: their complexity and vivacity make them fit materials. But a man has no such power over any of his other ideas, whether of the external or internal senses: he cannot, after the utmost effort, combine these into new forms: his ideas of such objects are too obscure for this operation. An image thus fabricated cannot be called a secondary perception, not being derived from an original perception: the poverty of language however, as in the case immediately above mentioned, has occasioned the same term idea to be apply’d to all. This singular power of fabricating images independent of real objects, is distinguished by the name imagination.
19. As ideas are the chief materials employ’d in thinking, reasoning, and reflecting, it is of consequence that their nature and differences be understood. It appears now, that ideas may be distinguished into three kinds; first, Ideas or secondary perceptions, properly termed ideas of memory; second, Ideas communicated by language or other signs; and, third, Ideas of imagination. These ideas differ from each other in many respects; but the chief foundation of the distinction is the difference of their causes. The first kind are derived from real existences that have been objects of our senses: language is the cause of the second, or any other sign that has the same power with language; and a man’s imagination is to himself the cause of the third. It is scarce necessary to add, that an idea, originally of imagination, being convey’d to others by language or any other vehicle, becomes in the mind of those to whom it is convey’d an idea of the second kind; and again, that an idea of this kind, being afterward recalled to the mind, becomes in that circumstance an idea of memory.
20. Human nature is not so constituted, as that its objects are perceived with indifferency: these, with very few exceptions, raise in us either pleasant or painful emotions. External objects, at the same time, appear in themselves agreeable or disagreeable; but with some difference betwixt those which produce organic impressions, and those which affect us from a distance. When we touch a soft and smooth body, we have a pleasant feeling as at the place of contact; and this feeling we distinguish not, at least not accurately, from the agreeableness of the body itself. The same holds in general with regard to all the organic impressions. It is otherwise in hearing and seeing. A sound is perceived as in itself agreeable; and, at the same time, raises in the hearer a pleasant emotion: an object of sight appears in itself agreeable; and, at the same time, raises in the seer a pleasant emotion. These are accurately distinguished. The pleasant emotion is felt as within the mind: the agreeableness of the object is placed upon the object, and is perceived as one of its qualities or properties. The agreeable appearance of an object of sight, is termed beauty; and the disagreeable appearance of such an object is termed ugliness.
21. But though beauty and ugliness, in their proper and genuine signification, are confined to objects of sight; yet in a more lax and figurative signification, they are apply’d to objects of the other senses. They are sometimes apply’d even to abstract terms; for it is not unusual to say, a beautiful theorem, a beautiful constitution of government. But I am inclined to think, that we are led to use such expression by conceiving the thing as delineated upon paper, and as in some sort an object of sight.
22. A line composed by a precise rule, is perceived and said to be regular. A straight line, a parabola, a hyperbola, the circumference of a circle, and of an ellipse, are all of them regular lines. A figure composed by a precise rule, is perceived and said to be regular. Thus a circle, a square, a hexagon, an equilateral triangle, are regular figures, being composed by a rule that determines the form of each. When the form of a line or of a figure is ascertained by a rule that leaves nothing arbitrary, the line and the figure are said to be perfectly regular: this is the case of the figures now mentioned; and it is the case of a straight line and of the circumference of a circle. A figure and a line are not perfectly regular where any part or circumstance is left arbitrary. A parallelogram and a rhomb are less regular than a square: the parallelogram is subjected to no rule as to the length of sides, other than that the opposite sides be equal: the rhomb is subjected to no rule as to its angles, other than that the opposite angles be equal. For the same reason, the circumference of an ellipse, the form of which is susceptible of much variety, is less regular than that of a circle.
23. Regularity, properly speaking, belongs, like beauty, to objects of sight: like beauty, it is also apply’d figuratively to other objects. Thus we say, a regular government, a regular composition of music, and, regular discipline.
24. When two figures are composed of similar parts, they are said to be uniform. Perfect uniformity is where the constituent parts of two figures are precisely similar to each other. Thus two cubes of the same dimensions are perfectly uniform in all their parts. An imperfect uniformity is, where the parts mutually correspond, but without being precisely similar. The uniformity is imperfect betwixt two squares or cubes of unequal dimensions; and still more so betwixt a square and a parallelogram.
25. Uniformity is also applicable to the constituent parts of the same figure. The constituent parts of a square are perfectly uniform: its sides are equal and its angles are equal. Wherein then differs regularity from uniformity? for a figure composed of similar or uniform parts must undoubtedly be regular. Regularity is predicated of a figure considered as a whole composed of resembling or uniform parts: uniformity again is predicated of these parts as related to each other by resemblance. We say, a square is a regular, not an uniform figure: but with respect to the constituent parts of a square, we say not that they are regular, but that they are uniform.
26. In things destined for the same use, as legs, arms, eyes, windows, spoons, we expect uniformity. Proportion ought to govern parts intended for different uses. We require a certain proportion betwixt a leg and an arm; in the base, the shaft, the capital, of a pillar; and in the length, the breadth, the height, of a room. Some proportion is also required in different things intimately connected, as betwixt a dwelling-house, the garden, and the stables. But we require no proportion among things slightly connected, as betwixt the table a man writes on and the dog that follows him. Proportion and uniformity never coincide: things perfectly similar are uniform; but proportion is never applied to them: the four sides and angles of a square are equal and perfectly uniform; but we say not that they are proportional. Thus, proportion always implies inequality or difference; but then it implies it to a certain degree only: the most agreeable proportion resembles a maximum in mathematics; a greater or less inequality or difference is less agreeable.
27. Order regards various particulars. First, in tracing or surveying objects, we are directed by a sense of order: we conceive it to be more orderly, that we should pass from a principle to its accessories and from a whole to its parts, than in the contrary direction. Next, with respect to the position of things, a sense of order directs us to place together things intimately connected. Thirdly, in placing things that have no natural connection, that order appears the most perfect, where the particulars are made to bear the strongest relation to each other that position can give them. Thus parallelism is the strongest relation that position can bestow upon straight lines. If they be so placed as by production to intersect each other, the relation is less perfect. A large body in the middle and two equal bodies of less size, one on each side, is an order that produces the strongest relation the bodies are susceptible of by position. The relation betwixt the two equal bodies would be stronger by juxtaposition; but they would not both have the same relation to the third.