We call that sublime which is absolutely great

Immanuel Kant

Whatever is fitted in any sort to excite the ideas of pain, and danger, that is to say, whatever is in any sort terrible, or is conversant about terrible objects, or operates in a manner analogous to terror, is a source of the sublime; that is, it is productive of the strongest emotion which the mind is capable of feeling

Edmund Burke

A tree, the height of which we estimate with reference to the height of a man, at all events gives a standard for a mountain; if this were a mile high, it would serve as unit for the number expressive of the earth's diameter, so that the latter might be made intuitible. The earth's diameter would supply a unit for the known planetary system; this again for the Milky Way; and the immeasurable number of Milky Way systems called nebulae, which presumably constitute a system of the same kind among themselves, lets us expect no bounds here. Now the sublime in the aesthetical judging of an immeasurable whole like this lies, not so much in the greatness of the number of units, as in the fact that in our progress we ever arrive at yet greater units

Immanuel Kant

The feeling of the Sublime is therefore a feeling of pain arising from the want of accordance between the aesthetical estimation of magnitude formed by the Imagination and the estimation of the same formed by Reason.

Immanuel Kant