Theorems. THE Beauty of Theorems, or universal Truths demonstrated, deserves a distinct Consideration, being of a Nature pretty different from the former kinds of Beauty; and yet there is none in which we shall see such an amazing Variety with Uniformity: and hence arises a very great Pleasure distinct from Prospects of any farther Advantage.
For in one Theorem we may find included, with the most exact Agreement, an infinite Multitude of particular Truths; nay, often an Infinity of Infinites: so that altho' the Necessity of forming abstract Ideas, and universal Theorems, arises perhaps from the Limitation of our Minds, which cannot admit an infinite Multitude of singular Ideas or Judgments at once, yet this Power gives us an Evidence of the Largeness of the human Capacity above our Imagination. Thus for instance, the 47th Proposition of the first Book of Euclid's Elements contains an infinite Multitude of Truths, concerning the infinite possible Sizes of right-angled Triangles, as you make the Area greater or less; and in each of these Sizes you may find an infinite Multitude of dissimilar Triangles, as you vary the Proportion of the Base to the Perpendicular; all which Infinitys of Infinites agree in the general Theorem. In Algebraick, and Fluxional Calculations, we shall still find a greater Variety of particular Truths included in general Theorems; not only in general Equations applicable to all Kinds of Quantity, but in more particular Investigations of Areas and Tangents: In which one Manner of Operation shall discover Theorems applicable to infinite Orders or Species of Curves, to the infinite Sizes of each Species, and to the infinite Points of the infinite Individuals of each Size.
Foundation of their Beauty. That we may the better discern this Agreement, or Unity of an Infinity of Objects, in the general Theorem, to be the Foundation of the Beauty or Pleasure attending their Discovery, let us compare our Satisfaction in such Discoveries, with the uneasy state of Mind in which we are, when we can only measure Lines, or Surfaces, by a Scale, or are making Experiments which we can reduce to no general Canon, but only heaping up a Multitude of particular incoherent Observations. Now each of these Trials discovers a new Truth, but with no Pleasure or Beauty, notwithstanding the Variety, till we can discover some sort of Unity, or reduce them to some general Canon.
Little Beauty in Axioms. Again, let us take a Metaphysical Axiom, such as this, Every Whole is greater than its Part; and we shall find no Beauty in the Contemplation. For tho' this Proposition contains many Infinitys of particular Truths; yet the Unity is inconsiderable, since they all agree only in a vague, undetermin'd Conception of Whole and Part, and in an indefinite Excess of the former above the latter, which is sometimes great and sometimes small. So, should we hear that the Cylinder is greater than the inscrib'd Sphere, and this again greater than the Cone of the same Altitude and Diameter with the Base, we shall find no pleasure in this Knowledge of a general Relation of greater and less, without any precise Difference or Proportion. But when we see the universal exact Agreement of all possible Sizes of such Systems of Solids, that they preserve to each other the constant Ratio of 3, 2, 1; how beautiful is the Theorem, and how are we ravish'd with its first Discovery!
Easy Theorems. We may likewise observe, that easy or obvious Propositions, even where the Unity is sufficiently distinct, and determinate, do not please us so much as those, which being less obvious, give us some Surprize in the Discovery: Thus we find little Pleasure in discovering that a Line bisecting the vertical Angle of an Isosceles Triangle, bisects the Base, or the Reverse; or, that Equilateral Triangles are Equiangular. These Truths we almost know Intuitively, without Demonstration: They are like common Goods, or those which Men have long possessed, which do not give such sensible Joys as much smaller new Additions may give us. But let none hence imagine, that the sole Pleasure of Theorems is from Surprize; for the same Novelty of a single Experiment does not please us much: nor ought we to conclude from the greater Pleasure accompanying a new, or unexpected Advantage, that Surprize, or Novelty is the only Pleasure of Life, or the only ground of Delight in Truth. Another kind of Surpirze in certain Theorems increases our Pleasure above what we have in Theorems of greater Extent; when we discover a general Truth, which upon some confused Notion we had reputed false: as that Assymptotes always approaching should never meet the Curve. This is like the Joy of unexpected Advantage where we dreaded Evil. But still the Unity of many Particulars in the general Theorem is necessary to give Pleasure in any Theorem.
Corollarys. There is another Beauty in Propositions, when one Theorem contains a great Multitude of Corollarys easily deducible from it. Thus that Theorem which gives us the Equation of a Curve, whence perhaps most of its Propertys may be deduc'd, does some way please and satisfy our Mind above any other Proposition: Such a Theorem also is the 35th of the 1st Book of Euclid, from which the whole Art of measuring right-lin'd Areas is deduc'd, by Resolution into Triangles, which are the halfs of so many Parallelograms; and these are each respectively equal to so many Rectangles of the Base into the perpendicular Altitude: The 47th of the 1st Book is another of like Beauty, and so are many others.
In the search of Nature there is the like Beauty in the Knowledge of some great Principles, or universal Forces, from which innumerable Effects do flow. Such is Gravitation, in Sir Isaac Newton's Scheme; such also is the Knowledge of the Original of Rights, perfect and imperfect, and external; alienable and unalienable, with their manner of Translations; from whence the greatest Part of moral Dutys may be deduc'd in the various Relations of human Life.
It is easy to see how Men are charm'd with the Beauty of such Knowledge, besides its Usefulness; and how this sets them upon deducing the Propertys of each Figure from one Genesis, and demonstrating the mechanick Forces from one Theorem of the Composition of Motion; even after they have sufficient Knowledge and Certainty in all these Truths from distinct independent Demonstrations. And this Pleasure we enjoy even when we have no Prospect of obtaining any other Advantage from such Manner of Deduction, than the immediate Pleasure of contemplating the Beauty: nor could Love of Fame excite us to such regular Methods of Deduction, were we not conscious that Mankind are pleas'd with them immediately, by this internal Sense of their Beauty.
Fantastick Beauty. It is no less easy to see into what absurd Attempts Men have been led by this Sense of Beauty, and a silly Affectation of obtaining it in the other Sciences as well as the Mathematicks. 'Twas this probably which set Descartes on that hopeful Project of deducing all human Knowledge from one Proposition, viz. Cogito, ergo sum; while others with as little Sense contended, that Impossibile est idem simul esse & non esse, had much fairer Pretensions to the Style and Title of Principium humanae Cognitionis absolutè primum. Mr. Leibnitz had an equal Affection for his favourite Principle of a sufficient Reason for every thing in Nature, and brags to Dr. Clarke of the Wonders he had wrought in the intellectual World by its Assistance; but his learned Antagonist seems to think he had not sufficient Reason for his Boasting[1]. If we look into particular Sciences, we may see in the Systems learned Men have given us of them, the Inconveniences of this Love of Uniformity. How aukwardly is Puffendorf forc'd to deduce the several Dutys of Men to God, themselves, and their Neighbours, from his single fundamental Principle of Sociableness to the whole Race of Mankind? This Observation might easily be extended farther, were it necessary; and is a strong Proof, that Men perceive the Beauty of Uniformity in the Sciences, even from the Contortions of common Sense they are led into by pursuing it.
This Delight which accompanys Sciences, or universal Theorems, may really be call'd a kind of Sensation; since it necessarily accompanys the Discovery of any Proposition, and is distinct from bare Knowledge itself[2], being most violent at first, whereas the Knowledge is uniformly the same. And however Knowledge enlarges the Mind, and makes us more capable of comprehensive Views and Projects in some kinds of Business, whence Advantage may also arise to us; yet we may leave it in the Breast of every Student to determine, whether he has not often felt this Pleasure without any such prospect of Advantage from the Discovery of his Theorem. All which can thence be infer'd is only this, that as in our external Senses, so in our internal ones, the pleasant Sensations generally arise from those Objects which calm Reason would have recommended, had we understood their Use, and which might have engag'd our pursuits from Self-Interest.
Works of Art. As to the Works of Art, were we to run thro' the various artificial Contrivances or Structures, we should constantly find the Foundation of the Beauty which appears in them, to be some kind of Uniformity, or Unity of Proportion among the Parts, and of each Part to the Whole. As there is a great Diversity of Proportions possible, and different Kinds of Uniformity, so there is room enough for that Diversity of Fancys observable in Architecture, Gardening, and such like Arts in different Nations; they all may have Uniformity, tho' the Parts in one may differ from those in another. The Chinese or Persian Buildings are not like the Grecian and Roman, and yet the former has its Uniformity of the various Parts to each other, and to the Whole, as well as the latter. In that kind of Architecture which the Europeans call Regular, the Uniformity of Parts is very obvious, the several Parts are regular Figures, and either equal or similar at least in the same Range; the Pedestals are Parallelopipedons or square Prisms; the Pillars, Cylinders nearly; the Arches circular, and all those in the same Row equal; there is the same Proportion every-where observ'd in the same Range between the Diameters of Pillars and their Heights, their Capitals, the Diameters of Arches, the Heights of the Pedestals, the Projections of the Cornice, and all the Ornaments in each of our five Orders. And tho' other Countrys do not follow the Grecian or Roman Proportions; yet there is even among them a Proportion retain'd, a Uniformity, and Resemblance of corresponding Figures; and every Deviation in one part from that Proportion which is observ'd in the rest of the Building, is displeasing to every Eye, and destroys or diminishes at least the Beauty of the Whole.
The same might be observ'd thro' all other Works of Art, even to the meanest Utensil; the Beauty of every one of which we shall always find to have the same Foundation of Uniformity amidst Variety, without which they appear mean, irregular and deform'd.
See the Letters which pass'd between Dr. Clarke and Mr. Leibnitz, Pag. 23.
Aristotle (Ethic. Nicom. I. ro. c. 3.) justly observes, that we have certain natural Propensitys to certain Actions, or to the Exercise of certain natural Powers, without a View to, or Intention of, obtaining those Pleasures which naturally accompany them. Περὶ πολλὰ σπουδὴν ποιησαίμεϑα ἂν, καὶ εἰ μηδεμίαν ἐπιϕέϱοι ἡδονήν, οἰ̑ον ὀϱα̑ν, μνημονεύειν, εἰδέναι, τὰς ἀϱετὰς ἔχειν· εἰ δ' ἐξ ἀνάγκης ἕπονται τουτοις ἡδοναὶ, οὐδὲν διαϕέϱει· ἑλοίμεϑα γὰϱ ἂν ταυ̑τα, καὶ εἰ μὴ γένοιτ' ἂν ἀπ' αὐτω̑ν ἡδονή.