Some of the things suggested by the sensations of sight, as extension and figure, are suggested so instantaneously, that they appear to be objects of sight, things actually seen. But this important law of our nature, by which so many things appear to be seen, which are only suggested by the feelings of sight, it requires the knowledge of other elements of the mental phenomena to explain.
The imperfections of the language, by which we have to speak of the phenomena of sight, deserve the greatest attention.
We have an appropriate name for the organ; it is the Eye. And we have an appropriate name for the Object; it is light. But we have no appropriate name for the Sensation. From confusion of names, proceeds confusion of ideas. And from misnaming, on this one point, not a little unprofitable discourse on the subject of the human mind has been derived.
The word sight, in certain phrases, denotes the sensation. If I am asked, what is the feeling which I have by the eye? I answer, sight. But sight is also a name of the object. The light of day is said to be a beautiful sight. And sight is sometimes employed as a name of the organ. An old man informs us, 23 that his sight is failing, meaning that his eyes are failing.[5]
[5] The example given does not seem to me to prove that sight is ever employed as a name of the organ. When an old man says that his sight is failing, he means only that he is less capable of seeing. His eyes might be failing in some other respect, when he would not say that his sight was failing. The term “sense of sight,” like sense of hearing or of smell, stands, as it seems to me, for the capability, without reference to the organ.—Ed.
Colour is a name, as well of the object, as of the sensation. It is most commonly a name of the object. Colour is, properly speaking, a modification of light, though it is never conceived but as something spread over a surface; it is, therefore, not the name of light simply, but the name of three things united, light, surface, and a certain position of the two. In many cases, however, we have no other name for the sensation. If I am asked, what feeling I have when a red light is presented to my eyes, I can only say, the colour of red; and so of other visual feelings, the colour of green, the colour of white, and so on.
In the term sense of sight, the same complexity of meaning is involved which we have observed in the terms sense of smell, and sense of hearing. When I speak of my sense of sight, as when I speak of the attraction of the load-stone, I mean to denote an antecedent, and a consequent; the organ with its object in appropriate position, the antecedent; the sensation, the consequent. This is merely the philosophical statement of the fact, that, when light is received into the eye, the sensation of sight is the consequence.
Vision, a word expressive of the phenomena of 24 sight, is ambiguous in the same manner. It is sometimes used to denote the sense of seeing; that is, the antecedent and consequent, as explained in the preceding paragraph. Thus we say, the phenomena of vision, with the same propriety as we say the phenomena of sight. It is sometimes employed to denote the sensation. If we ask what feeling a blind man is deprived of, it would be perfectly proper to say, vision is the feeling of which he is deprived. It is, also, employed to denote the object. What vision was that? would be a very intelligible question, on the sudden appearance and disappearance of something which attracted the eye.[6]
[6] Vision, I believe, is used to denote the object of sight, only when it is supposed that this object is something unreal, i.e., that it has not any extended and resisting substance behind it: or rhetorically, to signify that the object looks more like a phantom than a reality; as when Burke calls Marie Antoinette, as once seen by him, a delightful vision.—Ed.