The better to conceive the ideas we receive from sensation, it may not be amiss for us to consider them, in reference to the different ways whereby they make their approaches to our minds, and make themselves perceivable by us.
First, Then, there are some which come into our minds by one sense only.
Secondly, There are others that convey themselves into the mind by more senses than one.
Thirdly, Others that are had from reflection only.
Fourthly, There are some that make themselves way, and are suggested to the mind by all the ways of sensation and reflection.
We shall consider them apart under their several heads.
Ideas of one sense, as colours, of seeing; sound, of hearing;
First, There are some ideas which have admittance only through one sense, which is peculiarly adapted to receive them. Thus light and colours, as white, red, yellow, blue, with their several degrees or shades and mixtures, as green, scarlet, purple, sea-green, and the rest, come in only by the eyes: all kinds of noises, sounds, and tones, only by the ears: and several tastes and smells, by the nose and palate. And if these organs, or the nerves, which are the conduits to convey them from without to their audience in the brain, the mind’s presence-room (as I may so call it) are any of them so disordered, as not to perform their functions, they have no postern to be admitted by; no other way to bring themselves into view, and be perceived by the understanding.
The most considerable of those belonging to the touch are heat and cold, and solidity: all the rest, consisting almost wholly in the sensible configuration, as smooth and rough, or else more or less firm adhesion of the parts, as hard and soft, tough and brittle, are obvious enough.
I think, it will be needless to enumerate all the particular simple ideas, belonging to each sense. Nor indeed is it possible, if we would; there being a great many more of them belonging to most of the senses, than we have names for. The variety of...