Sir Isaac Newton
One of Newton's most controversial claims was that motion and rest are absolute, i.e. that any body is really either moving or at rest, regardless of its relation to other bodies. Absolute motion and rest were defined by the relation of a body to absolute space and time.
From Scholium to the Definitions, Principia Mathematica
I do not define time, space, place, and motion, as being well known to all. Only I must observe that the common people conceive those quantities under no other notions but from the relation they bear to sensible objects. And thence arise certain prejudices, for the removing of which it will be convenient to distinguish them into absolute and relative, true and apparent, mathematical and common.
1. Absolute, true, and mathematical time, of it self and from its own nature, flows equably without relation to anything external, and by another name is called 'duration'; relative, apparent, and common time is some sensible and external (whether accurate or unequable) measure of duration by means of motion, which is commonly used instead of true time, such as an hour, a day, a month, a year.
2. Absolute space, in its own nature, without relation to anything external, remains alwayas similar and immovable. Relative space is some movable dimension or measure of the absolute spaces, which our senses determine by its position to bodies and which is commonly taken for immovable space; such is the dimenion of a subterraneous, an aerial, or celestial space, determined by its position in respect of the earth.
George Berkeley was an early critic of the concepts of absolute space and time. The following is from De Motu, a work accessible to Kant.
"Again, that space is infinite, immoveable, indivisible, insensible, without relation and without distinction. That is, all its attributes are privative or negative. It seems therefore to be mere nothing. The only slight difficulty arising is that it is extened, and extension is a positive quality. But what sor of extension, I ask, is that which cannot be divided nor measured, no part of whic hcan be perceived by sense or pictured by the imagination? . . . Pure intellect, too, knows nothing of absolute space. That faculty is concerned only wiht spiritual and inextended things, such as our mints, their states, passions, virtues, and such like. From absolute space then let us take away now the words of the name, and nothing will remain in sense, imagination, or intellect. Nothing else then is denoted by those words than pure privation or negation, i.e. mere nothing" (Section 53).
Berkeley's remarks are closely paralleled by Kant's. "Those, on the other hand, who maintain the absolute reality of space and time, whether as self-subsistent or only as inherent, must come into conflict with the principles of experience itself. For it fhey decide the former alternative (which is generally the view taken by mathematical students of nature), they have to admit two eternal and infinite nonentities (space and time) which are there (yet without being anything real) only in order to contain in themselves all that is real" (A39/B56).
"For if we regard space and time as properties which, if they are to be possible at all, must be found in things in themselves, and if we reflect on the absurdities which are then involved, in that two infinite things, which are not substances, nor anything actually inhering in substances, must yet have existence, nay, must be the necessary condition for the existence of all things, and moreover must continue to exist, even although all existing things be removed,--we cannot blame the good Berkeley for degrading bodies to mere illusion" (B70-1).
From Scholium to the Definitions, Principia Mathematica
But because the parts of space cannot be seen or distinguished from one another by our senses, therefore in their stead we use sensible measures of them. For from the positions and distances of things from any body considerd as immovable we define all motions, considering bodies as transferred from some of those places into others. And so, instead of absolute places and motions, we use relative ones, and that witout any inconvenience in common affairs; but in philosophical disquisitions, we ought to abstract from our senses and consider things themselves, distinct from what are only sensible measures of them. For it may be that there is no body really at rest to which the places and motions of others may be referred.
Compare these passages from the Critique, where the imperceivability of time is a crucial premise in the second-edition proofs of the principle of substantiality (First Analogy) and the principle of causality (Second Analogy):
"Now time cannot by itself be perceived. Consequently, there must be found in the objects of perception, that is, the appearances, the substratum which represents time in general; and all change or coexistence must, in being apprehended, be perceived in this substratum, and through the relations of the appearances to it" (B225).
"For time cannot be perceived in itself, and what precedes and what follows cannnot, therefore, by relation to it, be empirically determined in the object. I am conscious only that my imagination sets the one state before and the other after, not that the one state precedes the other in the object" (B233).
"Absolute time is not an object of perception with which appearances could be confronted" (A217/B264).
Leibniz's criticism (Third Paper to Clarke, Section 5.)
If space was an absolute being, there would something happen for which it be impossible there should be a sufficient reason. Which is against my axiom. And I prove it thus. Space is something absolutely uniform; and, without the things placed in it, one point of space does not absolute differ in any respect whatsoever from another point of space. Now from hence it follows, (supposing space to be something in itself, besides the order of bodies among themselves,) that 'tis impossible there should be a reason, why God, preserving the same situations of bodies among themselves, should have placed them in space after one certain particular manner, and not otherwise; why every thing was not placed the quite contrary way, for instance, by changing East into West.
For Leibniz's positive view of space, click here .
From the General Scholium to Principia Mathematica
. . . the true God is a living, intelligent, and powerful Being; and, from his other perfections, that he is supreme or most perfect. He is eternal and infinite, omnipotent and omniscient; that is, his duration reaches from eternity to eternity; his presence from infinitey to infinity; he governs all things and knows all things that are or can be done. He is not eternity and infinity, but eternal and infinite; he is not duration or space, but he endures and is present. He endures forever and is everywhere present; and by existing always and everywhere, he constitutes duration and space. Since every particle of space is always and every indivisible moment of duration is everywhere, certainly the Maker and Lord of all things cannot be never and nowhere.
Leibniz's criticism (Third Paper to Clarke, Section 3.)
These gentlemen maintain therefore, that space is a real absolute being. But this involves them in great difficulties; for such a being must needs be eternal and infinite. Hence some have believed it to be God himself, or, one of his attributes, his immensity. But since space consists of parts, it is not a thing which can belong to God.
