both cases the effect may take place without the organ leaving the normal state; for example, a strong salt flavour prevents the perception of a sweet flavour which would be perceived in the absence of the first; strongly sugared water renders insensible the flavour of a slightly sugared water drunk after it.

(987.) But if the analogy of the preceding facts with those which relate to the senses of seeing and hearing is evident, we must own that in our day we know of none that correspond to the contrast of difference, in virtue of which two tones of the same scale of colour appear to the eye more different than they really are. To establish this correspondence, it is necessary we should demonstrate, in the case of simultaneity, that two flavours, proceeding from two matters differing in taste, placed on distinct parts of the tongue, differ more than they would if they proceeded from matters differing less in taste. Finally, in the case of succession, it is necessary to show, that two flavours perceived successively would present more difference than if they had been perceived separately, supposing that we are able to retain for some time the recollection of the first flavour.

(988.) Experiments on the contrast of difference of flavours ought to be made:

1o. With the same kind of flavoured substance taken in different quantities;

2o. With two different bodies having the same generic flavour, as cane-sugar, grape-sugar, manna;

3°. With bodies possessed of different flavours, such as sugar, marine salt, citric acid, &c.

Is there a Contrast of Antagonism in Taste?

(989.) Knowing nothing that bears a resemblance to antagonism in the sensations of taste, we cannot cite any fact suitable to exhibit either a simultaneous or successive contrast of antagonism in flavours.

OF SMELL.

(990.) All that I have said on the contrast of taste is applicable to the contrasts of smell: we can, by analogy, admit of a contrast of difference, either simultaneous or successive, for odours, but nothing in the perceptions we receive from it corresponds to the contrast of antagonism.

CONCLUSION OF THIS SECTION.

(991.) It follows from what I have said in this section, 1°. That the senses of seeing, hearing, smell, and, I may add, the sense of touch, all present, as I have before remarked, the phenomenon of not recognising a weak impression which is received at the same time as a much stronger

one.

2o. That the result is the same when the weak impression immediately, or almost immediately, succeeds the strong one.

3°. That the two preceding phenomena may be observed when the strongest impression does not sufficiently disturb the organ experiencing them, as to admit of our considering the latter as being in an abnormal state.

4°. That if we can deduce these phenomena of a contrast of difference, nevertheless we must own that it will be difficult to quote results from experiments adapted to show clearly that in the simultaneous or successive perception of two sounds, two flavours, and two odours, we remark between the two sensations a greater difference than we should detect if the two sounds, flavours, and odours were less different from each other.

5°. That at the present time we have no idea of what a contrast of antagonism in the perception of sounds, flavours, and odours may be.

(992.) We have seen how the study of the contrasts of sight diffuses a light on the history of the other senses. In insisting on the differences of sounds and colours, I believe them to be based on truth; but my readers deceive them

selves if they think I believe that ulterior studies would add more to the differences I have remarked between sight on the one part, and hearing, smell, and taste on the other. In speaking of these differences, my intention has been to show clearly that in the present state of our knowledge we have no actual experimental proof which establishes that hearing, smell, and taste, are submitted to simultaneous and successive contrasts corresponding to the contrasts of difference and antagonism which exist in the phenomena of the sight of white, black, and coloured bodies; it does not signify if future researches cannot demonstrate the existence of these affinities: besides, if I did not fear to go in advance of the result of experiments which, although commenced more than twenty years since,* are still far from being terminated, I would say that I should be more disposed to admit affinities than to reject them (974.).

§ 4.

THE LIGHT WHICH THE STUDY OF CONTRAST APPEARS TO ME SUSCEPTIBLE OF SHEDDING UPON SEVERAL OTHER PHENOMENA OF THE UNDER

STANDING.

(993.) If it is difficult, at the present day, to experimentally demonstrate that in hearing, tasting, and smelling, there exist definite contrasts of as precise a nature as the various contrasts affecting us through the organ of sight,yet the examination of these latter, in giving the first experimental proof of this fact, that two different objects, placed side by side, appear by the comparison more different than they really are, and in placing in its proper aspect a phenomenon generally spoken of under the name of contrast of colours, without knowing either its extent or its importance, -seems to me adapted to throw a light on the study of several of the operations of the human mind.

In fact, when certain persons regard two objects under a relation of difference, does it not happen that the difference exaggerates itself, so to speak, unknown to them, precisely

*This was written in 1838.

as it happens in regarding two juxtaposed colours, in which all that is analogous between the two colours disappears in a greater or less degree? Does it not happen that these persons, but little accustomed to reflect on the operations of the mind, give themselves up to the judgment they first brought to bear, always retaining some inexact ideas which they would have been able to rectify, in considering objects under new relations adapted to control their first opinion? Are they not in the position of one who, having concluded, at first sight, that a difference of 150 yard exists between a measure of one yard placed beside a measure of two yards, preserves that opinion in his memory as correct, because, ignorant of the effect of contrast of size (965., 966.), nothing can make him feel the necessity of having recourse to a counter-proof to rectify his judgment, as he would have been. led to do had he possessed that knowledge, and moreover, had he felt the necessity for some motive of having exactly the difference of length of the two measures, for then he would have had recourse to measurement.

This example is very well adapted to the comprehension of my ideas respecting the inexactitude of a great number of opinions brought to bear upon certain objects which we compare in respect to qualities, properties, and attributes we have not measured.

(a) Operations of the Mind corresponding to the Contrast of simultaneous Difference.

(994.) The inaccuracy of judgment in question, consisting in the exaggeration of a difference between two objects compared, enters into the contrast of simultaneous difference, whenever the qualities, properties, and attributes we compare, belong to objects before our eyes, or rather to objects more or less remote, in space or time, and then our opinions bear on the notions that memory recals to us or tradition has transmitted.

(b) Operations of the Mind corresponding to the Contrast of successive Difference.

(995.) I am about to examine those mental operations which appear to me to correspond to the contrast of successive difference, because they refer to a comparison esta

blished between two objects seen in succession, or between an opinion at present maintained, and a contrary opinion held at some previous period.

(996.) A man easily susceptible of receiving impressions, who travels through a country for the first time, is much disposed to form exaggerated notions, because he is most struck with the differences between the objects he now sees and those which have been presented to him previously in the country where he has long resided. The best method of correcting his judgment, is to revisit in succession the objects compared, and to bestow particular attention upon those qualities which have struck him the most forcibly, that he may regulate his first impression by newly-formed opinions.

(997.) Finally, is not our disposition of mind with regard to an opinion that is entirely abandoned for another, remarkable for this,-that we almost always form an exaggerated judgment of the opinion we have abandoned in the sense least favourable to it, and that hence the mind gives way to an exaggeration of the difference ?

Influence exercised by the Condition of our Organs upon many Operations of the Understanding.

(998.) In reflecting upon the condition of our organs under three circumstances, as follows:

1o. When the difference produced by the simultaneous contrast of two tints is carried to its maximum ;

2o. When a small object ceases to be perceptible on account of its proximity with a larger;

3°. When in looking at an object, which, however, is not very complex, we perceive, in a given time, only a small number of relations under which it can be presented to the attention of most persons,

I have been led to explain to myself clearly the case in which our mind, when certain ideas have become more familiar to it than others, is led to regard the former to the exclusion of the latter.

(a) When the mind is at work in solitude upon a subject. (b) When a discussion is entered into by two persons. Let us examine these two conditions.