It will be remembered from the preceding book that knowledge in general belongs to the objectification of will at its higher grades, and sensibility, nerves, and brain, just like the other parts of the organised being, are the expression of the will at this stage of its objectivity, and therefore the idea which appears through them is also in the same way bound to the service of will as a means (μηχανη) for the attainment of its now complicated (πολυτελεστερα) aims for sustaining a being of manifold requirements. Thus originally and according to its nature, knowledge is completely subject to the will, and, like the immediate object, which, by means of the application of the law of causality, is its starting-point, all knowledge which proceeds in accordance with the principle of sufficient reason remains in a closer or more distant relation to the will. For the individual finds his body as an object among objects, to all of which it is related and connected according to the principle of sufficient reason. Thus all investigations of these relations and connections lead back to his body, and consequently to his will. Since it is the principle of sufficient reason which places the objects in this relation to the body, and, through it, to the will, the one endeavour of the knowledge which is subject to this principle will be to find out the relations in which objects are placed to each other through this principle, and thus to trace their innumerable connections in space, time, and causality. For only through these is the object _interesting_ to the individual, _i.e._, related to the will. Therefore the knowledge which is subject to the will knows nothing further of objects than their relations, knows the objects only so far as they exist at this time, in this place, under these circumstances, from these causes, and with these effects—in a word, as particular things; and if all these relations were to be taken away, the objects would also have disappeared for it, because it knew nothing more about them. We must not disguise the fact that what the sciences consider in things is also in reality nothing more than this; their relations, the connections of time and space, the causes of natural changes, the resemblance of forms, the motives of actions,—thus merely relations. What distinguishes science from ordinary knowledge is merely its systematic form, the facilitating of knowledge by the comprehension of all particulars in the universal, by means of the subordination of concepts, and the completeness of knowledge which is thereby attained. All relation has itself only a relative existence; for example, all being in time is also non-being; for time is only that by means of which opposite determinations can belong to the same thing; therefore every phenomenon which is in time again is not, for what separates its beginning from its end is only time, which is essentially a fleeting, inconstant, and relative thing, here called duration.