Now here however I must say, as Abélard once did: _si omnes patres sic, at ego non sic_: for, in opposition to this principle, however great may be its antiquity and universality, my doctrine maintains, that there are _not_ two origins of movement differing fundamentally from one another; that movement does _not_ proceed either from inside, when it is ascribed to the will, or from outside, when it is brought about by causes; but that both things are inseparable and take place simultaneously with every movement made by a body. For movement which is admitted to arise from the _will_, always presupposes a _cause_ also: this cause, in beings that have knowledge, is a _motive_; but without it, even in these beings, movement is impossible. On the other hand, the movement of a body which is admitted to have been brought about by an outward _cause_, is nevertheless in itself a manifestation of the _will_ of that body which has only been evoked by that cause. Accordingly there is only one, uniform, universal and exceptionless principle of all movement, whose inner condition is _will_ and whose outer occasion is _cause_, which latter may also take the form of a _stimulus_ or of a _motive_, according to the nature of the thing moved. All that is known to us of things in a merely empirical or _à posteriori_, way, is in itself _will_; whereas, so far as they can be determined _à priori_, things belong exclusively to _representation_, to mere phenomenon. Natural phenomena therefore become proportionately less easy to comprehend, the more distinctly the will manifests itself in them, _i.e._ the higher they stand on the scale of beings; whereas, they become more and more comprehensible the smaller the amount of their empirical content, because they remain more and more within the sphere of mere representation, the forms of which, known to us _à priori_, are the principle of comprehensibility. Accordingly, it is only so long as we limit ourselves to this sphere--that is to say, only when we have before us mere representation, mere form without empirical content--that our comprehension is complete and thorough: that is, in the _à priori_ sciences, Arithmetic, Geometry, Phoronomy and Logic. Here everything is in the highest degree comprehensible; our insight is quite clear and satisfactory: it leaves nothing to be desired, since we are even unable to conceive that anything could be otherwise than it is. This comes from our having here exclusively to do with the forms of our own intellect. Thus the more we are able to comprehend in a relation, the more it consists of mere phenomenon and the less it has to do with the thing in itself. Applied Mathematics, Mechanics, Hydraulics, &c. &c., deal with the lowest degrees of objectification of the will, in which the largest part still remains within the sphere of mere representation; nevertheless even here there is already an empirical element which stands in the way of