But before all things we must learn to distinguish will [_Wille_] (_voluntas_) from free-will [_Willkühr_] (_arbitrium_)[199] and to understand that the former can subsist without the latter; this however presupposes my whole philosophy. The will is called free-will when it is illumined by knowledge, therefore when the causes which move it are motives: that is, representations. Objectively speaking this means: when the influence from outside which causes the act, has a _brain_ for its mediator. A motive may be defined as an external stimulus, whose action first of all causes an _image_ to arise in the _brain_, through the medium of which the will carries out the effect proper--an outward action of the body. Now, in the human species however, the place of such an image as this may be taken by a conception drawn from former images of this kind by dropping their differences, which conception consequently is no longer perceptible, but merely denoted and fixed by words. As the action of motives accordingly does not depend upon contact, they can try their power on the will against each other: in other words, they permit a certain choice which, in animals, is limited to the narrow sphere of that which has _perceptible_ existence for them; whereas, in man, its range comprises the vast extent of all that is _thinkable_: that is, of his conceptions. Accordingly we designate as _voluntary_ those movements which are occasioned, not by _causes_ in the narrowest sense of the word, as in inorganic bodies, nor even by _mere stimuli_, as in plants, but by _motives_.[200] These motives however presuppose an _intellect_ as _their mediator_, through which causality here acts, without prejudice to its entire necessity in all other respects. Physiologically, the difference between stimulus and motive admits also of the following definition. The stimulus provokes _immediate_ reaction, which proceeds from the very part on which the stimulus has acted; whereas the motive is a stimulus that has to go a roundabout way through the brain, where its action first causes an image to arise, which then, but not till then, provokes the consequent reaction, which is now called an act of volition, and _voluntary_. The distinction between voluntary and involuntary movement does not therefore concern what is essential and primary--for this is in both cases the will--but only what is secondary, the rousing of the will's manifestation: it has to do with the determination whether _causes_ proper, _stimuli_ or _motives_ (_i.e._ causes having passed through the medium of knowledge) are the guidance under which that manifestation takes place. It is in human consciousness,--differing from that of animals by not only containing perceptible representations but also abstract conceptions independent of time-distinctions, which act simultaneously and collaterally, whereby deliberation, _i.e._ a conflict of motives, becomes possible--it is in human consciousness,