[236] The most intelligent birds are also birds of prey, wherefore many of them, especially falcons, are highly susceptible of training. [Add. to 3rd ed.] [237] That the negroes should have become the special victims of the slave-trade, is evidently a consequence of the inferiority of their intelligence compared with that of other human races; though this by no means justifies the fact. [Add. to 3rd ed.] Everywhere indeed intelligence depends in the first instance upon the cerebral system, and this stands in a necessary relation to the rest of the organism; therefore cold-blooded animals are greatly inferior to warm-blooded ones, and invertebrate animals to _vertebrata_. But the organism is precisely nothing but the will become visible, to which, as that which is absolutely _prius_, everything constantly refers. The needs and aims of that will give in each phenomenon the rule for the means to be employed, and these means must harmonize with one another. Plants have no self-consciousness because they have no power of locomotion; for of what use would self-consciousness be to them unless it enabled them to seek what was salutary and flee what was noxious to them? And conversely, of what use could power of locomotion be to them, as they have no self-consciousness with which to guide it. The inseparable duality of Sensibility and Irritability does not yet appear therefore in the plant; they continue slumbering in the reproductive force which is their fundament, and in which alone the will here objectifies itself. The sun-flower, and every other plant, wills for light; but as yet their movement towards light is not separate from their apprehension of it, and both coincide with their growth.--Human understanding, which is so superior to that of all other beings, and is assisted by Reason (the faculty for non-perceptible representations, _i.e._ for conceptions; reflection, thinking faculty), is nevertheless only just proportionate, partly to Man's requirements, which greatly surpass those of animals and multiply to infinity; partly to his entire lack of all natural weapons and covering, and to his relatively weaker muscular strength, which is greatly inferior to that of monkeys of his own size;[238] lastly also, to the slowness with which his race multiplies and the length of his childhood and life, which demand secure preservation of the individual. All these great requirements had to be satisfied by means of intellectual powers, which, for this reason, predominate in him. But we find the intellect secondary and subordinate everywhere, and destined exclusively to serve the purposes of the will. As a rule too, it always remains true to its destiny and subservient to the will. How nevertheless, it frees itself in particular instances from this bondage through an abnormal preponderance of cerebral life, whereby purely objective cognition becomes possible which may be enhanced to genius, I have shown at