II. Distance of it self In|visible.
III. Remote Di|stance per|ceiv'd ra|ther by Ex|perience, than by Sense.
IV. Near Di|stance thought to be percei|ved by the Angle of the Optic Axes.
V. Difference between this and the former manner of perceiving Distance.
VI. Also by Di|verging Rays.
VII. This de|pends not on Experi|ence.
VIII. These the common Accounts, but not sa|tisfactory.
IX. Some Ideas perceived by the me|diation of others.
X. No Idea which is not it self per|ceived, can be the means of perceiving another.
XI. Distance perceived by means of some other Idea.
XII. Those Lines and Angles mentioned in Optics, are not themselves perceiv'd.
XIII, Hence the Mind doth not perceive Distance by Lines and Angles
XIV. Also be|cause they have no re|al Exi|stence.
XV. And be|cause they are insuffi|cient to ex|plain the Phaenome|na.
XVI. The Ideas that sug|gest Di|stance are 1st. the Sen|sation ari|sing from the turn of the Eyes.
XVII. Betwixt which and Distance there is no necessary Connexion.
XVIII. Scarce room for Mistake in this mat|ter.
XIX. No regard had to the Angle of the Optic Axes.
XX. Judgment of Distance made with both Eyes, the Result of Experi|ence.
XXI. 2dly, Con|fusedness of Appear|ance.
XXII. This the occasion of those Judg|ments at|tributed to diverging Rays.
XXIII. Objection answer'd.
XXIV. What de|ceives the Writers of Optics in this mat|ter.
XXV. The Cause, why one I|dea may suggest ano|ther.
XXVI. This apply|ed to Con|fusion and Distance.
XXVII. 3dly, The straining of the Eye.
XXVIII. The Occa|sions which suggest Di|stance, have in their own Nature no Relation to it.
XXIX. A difficult Case propo|sed by Dr. Barrow as repugnant to all the known Theories.
XXX. This Case contradicts a receiv'd Principle in Catop|trics.
XXXI. It is shewn to agree with the Principles we have laid down.
XXXII. This Phae|nomenon Illustrated.
XXXIII. It confirms the Truth of the Principle whereby it is explain|ed.
XXXIV. Vision when Distinct, and when Confus'd.
XXXV. The diffe|rent Effects of Parallel, Diverging and Con|verging Rays.
XXXVI. How Con|verging, and Diver|ging Rays come to suggest the same Di|stance.
XXXVII. A Person extream Purblind wou'd judge a|right in the fore|mention'd Case.
XXXVIII. Lines and Angles why useful in Optics.
XXXIX. The not un|derstand|ing this, a cause of Mistake.
XL. A Query propos'd by Mr. Moly|neux in his Diop|trics, con|sider'd.
XLI. One Born Blind wou'd not at first have any Idea of Di|stance by Sight.
XLII. This not a|greeable to the com|mon Prin|ciples.
XLIII. The proper Objects of Sight, not without the Mind, nor the Images of any thing without the Mind.
XLIV. This more fully ex|plain'd.
XLV. In what Sense we must be un|derstood to see Distance and exter|nal Things.
XLVI. Distance and Things placed at a Distance, not other|wise per|ceived by the Eye than by the Ear.
XLVII. The Ideas of Sight more apt to be confoun|ded with the Ideas of Touch than those of Hearing are.
XLVIII. How this comes to pass.
XLIX. Strictly speaking, we never see and feel the same thing.
L. Objects of Sight twofold Mediate and Imme|diate.
LI. These hard to separate, in our Thoughts.
LII. The recei|ved Ac|counts of our percei|ving Mag|nitude by Sight false
LIII. Magnitude perceiv'd as imme|diately, as Distance.
LIV. Two kinds of sensible Extension, neither of which is infinitely Divisible.
LV. The Tangi|ble Magni|tude of an Object steddy, the Visible not.
LVI. By what means, Tan|gible Mag|nitude is perceiv'd by Sight.
LVII. This far|ther en|larged on.
LVIII. No necessa|ry Connexi|on between, Confusion or Faintness of Appear|ance, and small or great Mag|nitude.
LIX. The Tangi|ble Magni|tude of an Object, more heed|ed than the Visible; and why.
LX. An Instance of this.
LXI. Men do not Measure by Visible Feet or Inches.
LXII. No necessa|ry Conexi|on between Visible and Tangible Extension.
LXIII. Greater Vi|sible Mag|nitude might sig|nifie Lesser Tangible Magnitude
LXIV. The Judg|ments we make of Magnitude depend al|together on Experience
LXV. Distance and Mag|nitude seen as Shame or Anger.
LXVI. But we are prone to think o|therwise, and why.
LXVII. The Moon seems greater in the Hori|zon than in the Me|ridian.
LXVIII. The cause of this Phaenome|non, assign|ed.
LXIX. The Hori|zontal Moon, why greater at one time than ano|ther.
LXX. The Ac|count we have gi|ven, prov'd to be true.
LXXI. And con|firmed, by the Moon's appearing greater in a Mist.
LXXII. Objection answer'd.
LXXIII. The way wherein Faintness suggests greater Magnitude Illustrated.
LXXIV. Appear|ance of the Horizontal Moon, why thought difficult to explain.
LXXV. Attempts towards the Soluti|on of it made by several, but in vain.
LXXVI. The Opini|on of Dr. Wallis.
LXXVII. It is shewn to be unsa|tisfactory.
LXXVIII. How Lines and Angles may be of use in com|puting ap|parent Magni|tudes.
LXXIX. One born Blind, be|ing made to See, what Judgment he'd make of Magni|tude.
LXXX. The Mini|mum Vi|sibile the same to all Creatures.
LXXXI. Objection answer'd.
LXXXII. The Eye at all times, perceives the same number of visible Points.
LXXXIII Two Im|perfections in the Vi|sive Fa|culty.
LXXXIV Answering to which, we may conceive two Per|fections.
LXXXV. In neither of these two Ways do Microscopes improve the Sight.
LXXXVI The Case of Microscopi|cal Eyes, consider'd.
LXXXVII The Sight, admirably adapted to the ends of Seeing.
LXXXVIII Difficulty concerning Erect Vi|sion.
LXXXIX The com|mon way of explaining it.
XC. The same shewn to be false.
XCI. Not distin|guishing between I|deas of Sight and Touch, Cause of Mistake, in this Mat|ter.
XCII. The Case of one Born Blind, pro|per to be consider'd.
XCIII. Such a one might by Touch, at|tain to have Ideas of Upper and Low|er.
XCIV. Which Modes of Situation he'd attri|bute only to things Tangible.
XCV. He'd not at first Sight think any thing he saw, High or Low, E|rect or In|verted.
XCVI. This Illus|trated by an Exam|ple.
XCVII. By what means he'd come to de|nominate Visible Ob|jects high or low, &c.
XCVIII. Why he shou'd think those Objects highest, which are Painted on the lowest part of his Eye, and vice ver|sa.
XCIX. How he wou'd per|ceive by Sight the Situation of Exter|nal Objects.
C. Our propen|sion to think the contrary, no Argu|ment a|gainst what hath been said.
CIII. An Object cou'd not be known at first Sight by the Co|lour.
CIV. Nor by the Magnitude thereof.
CV. Nor by the Figure
CVI. In the first act of Visi|on, no Tan|gible Thing wou'd be suggested by Sight.
CVII. Difficulty proposed concerning Number.
CVIII. Number of things Vi|sible, wou'd not, at first Sight, sug|gest the like number of things Tan|gible.
CIX. Number the Crea|ture of the Mind.
CX. One Born Blind wou'd not at first Sight, num|ber Visible Things as others do.
CXI. The Situa|tion of any Object, de|termin'd with re|spect only to Objects of the same Sense.
CXII. No Di|stance great or small, between a Visible and Tangible Thing.
CXII. The not ob|serving this, cause of difficul|ty in Erect Vision,
CXIV. Which o|therwise includes nothing un|accounta|ble.
CXV. What is meant by the Pictures being in|verted.
CXVI. Cause of Mistake in this Mat|ter.
CXVII. Images in the Eye, not Pictures of external Objects.
CXVIII. In what Sense they are Pictures
CXIX. In this Af|fair we must care|fully di|stinguish between Ideas of Sight and Touch.
CXX. Difficult to explain by Words the true The|ory of Vi|sion.
CXXI. The Que|stion, whe|ther there is any Idea common to Sight and Touch, stated.
CXXII. Abstract Extension enquir'd into.
CXXIII. It is incom|prehensible.
CXXIV. Abstract Extension not the Ob|ject of Geo|metry.
CXV. The gene|ral Idea of a Triangle, consider'd.
CXXVI. Vacuum or pure Space, not com|mon to Sight and Touch.
CXXVII. There is no Idea or kind of I|dea, com|mon to both Senses.
CXXVIII. First Ar|gument in Proof here|of.
CXXIX. Second Ar|gument.
CXXX. Visible Fi|gure and Extension, not distinct Ideas from Colour.
CXXXI. Third Ar|gument.
CXXXII. Confirma|tion drawn from Mr. Moly|neux's Problem of a Sphere and a Cube, publish'd by Mr. Locke.
CXXXIII. Which is falsly sol|ved, if the common Supposition be true.
CXXXIV. More might be said in proof of our Tenent, but this suffices.
CXXXV. Farther Reflexion, on the fore|going Pro|blem.
CXXXVI The same thing doth not affect both Sight and Touch.
CXXXVII Tho same Idea of Mo|tion not common to Sight and Touch.
CXXXVIII The way wherein we apprehend Motion by Sight, easi|ly collected from what hath been said.
CXXXIX. Qu. How Visible and Tangible Ideas came to have the same Name if not of the same Kind.
CXL. This ac|counted for without supposing them of the same Kind.
CXLI. Obj. That a Tangible Square is liker to a Visible Square than to a Visible Cir|cle.
CXLII. Ans. That a Visible Square is fitter than a Visible Circle, to represent a Tangible Square.
CXLIII. But it doth not hence follow, that a Visible Square is like a Tan|gible Square.
CXLIV. Why we are more apt to confound Visible with Tan|gible I|deas, than other Signs with the Things sig|nify'd.
CXLV. Several o|ther Rea|sons hereof, assign'd.
CXLVI. Reluctancy in reject|ing any O|pinion, no Argument of its Truth.
CXLVII. Proper Ob|jects of Vi|sion, the Language of Nature.
CXLVIII In it there is much ad|mirable, and deser|ving our attention.
CXLIX. Question propos'd, concerning the Object of Geome|try.
CL. At first View, we are apt to think Visi|ble Exten|sion the Ob|ject of Geo|metry.
CLI. Visible Ex|tension shewn not to be the Ob|ject of Geo|metry.
CLII. Words may as well be thought the Object of Geometry, as Visible Extension.
CLIII. It is pro|pos'd to en|quire, what Progress an Intelligence that cou'd see, but not feel, might make in Geometry.
CLIV. He cannot understand those parts which re|late to So|lids, and their Sur|faces and Lines ge|nerated by their Secti|on.
CLV. Nor even the Ele|ments of plain Geo|metry.
CLVI. The proper Objects of Sight inca|pable of be|ing mana|ged as Geo|metrical Figures.
CLVII. The Opini|on of those who hold plain Fi|gures to be the imme|diate Ob|jects of Sight, con|sider'd.
CLVIII. Plains, no more the immediate Objects of Sight, than Solids.
CLIX. Difficult to enter pre|cisely in|to the Thoughts of the a|bove men|tion'd In|telligence.
CXL. The Object of Geome|try, its not being suffi|ciently un|derstood, cause of Difficulty and useless Labour in that Sci|ence.
Berkeley is most importantly a philosopher, the second of the three British Empiricists, following John Locke and preceding David Hume. AN ESSAY TOWARDS A NEW THEORY OF VISION was published in 1709, one year before his first important philosophical work, A TREATISE CONCERNING THE PRINCIPLES OF HUMAN KNOWLEDGE. Yet the ESSAY is not primarily a philosophical work. It is a study of visual perception which is best classed with experimental psychology. Its major objective is to show how we perceive the distance and size of objects and their spatial relation to other objects. In so doing, Berkeley manages to criticize most of the accepted views on the topic. The last part of the ESSAY is a consideration of the difference between perception by sight and by touch and of whether we ever perceive the same thing by both faculties. It is in his treatment of this latter issue that Berkeley hints at the philosophical doctrines which he soon elaborated.
Most of the standard discussions of vision in Berkeley’s day were couched in terms of geometric diagrams showing how light rays converged and diverged when they passed through lenses or were reflected from surfaces of varying curvature. It was claimed that distance was estimated on the basis of the angle at which light entered the eye. His criticisms of such views give the first insight into the special character of Berkeley’s concern. He says that the perception of distance cannot be explained by lines and angles because we never perceive any such things and those who know nothing of optics perceive distance without ever thinking of such lines and angles. Berkeley wants to know what we perceive immediately which allows us to say that something is near or far away. Nor will he allow us to say we perceive the distance between us and an object. We estimate it on the basis of our immediate perceptions. There are three we typically use: first, the sensation we get when we cross our eyes to see something very close; second, the confused appearance of an object as it gets close to the eye, and third, the muscular strain involved in preventing, temporarily, the confused appearance of an object close to the eye. In addition to these we use our knowledge of the size, number, kind, and so on, of the objects in question. There is no necessary connection between these perceptions and the distance of objects. We have found the connection in experience and this gives rise to a habitual or customary connection between these two kinds of ideas. Visual perceptions are signs of distance and are related to it in the way a blush is to shame, or a word to the idea it stands for.
The more usual features of Berkeley’s doctrine come to the fore when he explains how it is that we experience the visual sign and its connection with the distance it signifies. The idea of distance comes from touch. He insists that what we really mean when we say that an object is at a distance is that certain...
(The entire section is 1213 words.)