It does not lose this quality because it is only imaginary.

The horse that I imagine seems to have four legs, like a horse perceived.

As I call it before my mind, it seems as large as the real horse.

Neither the color, nor the size, nor the distribution of parts, nor any other attribute of the sort appears to be different in the imaginary object from what it is in the object as given in sensation.
The two experiences are, nevertheless, not the same; and every one knows that they are not the same.

One difference that roughly marks out the two classes of experiences from one another is that, as a rule, our sense-experiences are more vivid than are the images that exist in the imagination.
I say, as a rule, for we cannot always remark this difference.
Sensations may be very clear and unmistakable, but they may also be very faint and indefinite.