An act done by instinct differs from every other kind of act in that an understanding of its object does not precede it but follows upon it. Instinct is therefore a rule of action given à priori. We may be unaware of the object to which it is directed, as no understanding of it is necessary to its attainment. On the other hand, if an act is done by an exercise of reason or intelligence, it proceeds according to a rule which the understanding has itself devised for the purpose of carrying out a preconceived aim. Hence it is that action according to rule may miss its aim, while instinct is infallible.
On the à priori character of instinct we may compare what Plato says in the Philebus. With Plato instinct is a reminiscence of something which a man has never actually experienced in his lifetime; in the same way as, in the Phaedo and elsewhere, everything that a man learns is regarded as a reminiscence. He has no other word to express the à priori element in all experience.
There are, then, three things that are à priori:
(1) Theoretical Reason, in other words, the conditions which make all experience possible.
(2) Instinct, or the rule by which an object promoting the life of the senses may, though unknown, be attained.
(3) The Moral Law, or the rule by which an action takes place without any object.
Accordingly rational or intelligent action proceeds by a rule laid down in accordance with the object as it is understood. Instinctive action proceeds by a rule without an understanding of the object of it. Moral action proceeds by a rule without any object at all.
Theoretical Reason is the aggregate of rules in accordance with which all my knowledge—that is to say, the whole world of experience—necessarily proceeds. In the same manner Instinct is the aggregate of rules in accordance with which all my action necessarily proceeds if it meets with no obstruction. Hence it seems to me that Instinct may most appropriately be called practical reason, for like theoretical reason it determines the must of all experience.
The so-called moral law, on the other hand, is only one aspect of the better consciousness, the aspect which it presents from the point of view of instinct. This better consciousness is something lying beyond all experience, that is, beyond all reason, whether of the theoretical or the practical kind, and has nothing to do with it; whilst it is in virtue of the mysterious union of it and reason in the same individual that the better consciousness comes into conflict with reason, leaving the individual to choose between the two.
In any conflict between the better consciousness and reason, if the individual decides for reason, should it be theoretical reason, he becomes a narrow, pedantic philistine; should it be practical, a rascal.
If he decides for the better consciousness, we can make no further positive affirmation about him, for if we were to do so, we should find ourselves in the realm of reason; and as it is only what takes place within this realm that we can speak of at all it follows that we cannot speak of the better consciousness except in negative terms.
This shows us how it is that reason is hindered and obstructed; that theoretical reason is suppressed in favour of genius, and practical reason in favour of virtue. Now the better consciousness is neither theoretical nor practical; for these are distinctions that only apply to reason. But if the individual is in the act of choosing, the better consciousness appears to him in the aspect which it assumes in vanquishing and overcoming the practical reason (or instinct, to use the common word). It appears to him as an imperative command, an ought. It so appears to him, I say; in other words, that is the shape which it takes for the theoretical reason which renders all things into objects and ideas. But in so far as the better consciousness desires to vanquish and overcome the theoretical reason, it takes no shape at all; on the simple ground that, as it comes into play, the theoretical reason is suppressed and becomes the mere servant of the better consciousness. That is why genius can never give any account of its own works.
In the morality of action, the legal principle that both sides are to be heard must not be allowed to apply; in other words, the claims of self and the senses must not be urged. Nay, on the contrary, as soon as the pure will has found expression, the case is closed; nec audienda altera pars.
The lower animals are not endowed with moral freedom. Probably this is not because they show no trace of the better consciousness which in us is manifested as morality, or nothing analogous to it; for, if that were so, the lower animals, which are in so many respects like ourselves in outward appearance that we regard man as a species of animal, would possess some raison d'être entirely different from our own, and actually be, in their essential and inmost nature, something quite other than ourselves. This is a contention which is obviously refuted by the thoroughly malignant and inherently vicious character of certain animals, such as the crocodile, the hyaena, the scorpion, the snake, and the gentle, affectionate and contented character of others, such as the dog. Here, as in the case of men, the character, as it is manifested, must rest upon something that is above and beyond time. For, as Jacob Böhme says,  there is a power in every animal which is indestructible, and the spirit of the world draws it into itself, against the final separation at the Last Judgment. Therefore we cannot call the lower animals free, and the reason why we cannot do so is that they are wanting in a faculty which is profoundly subordinate to the better consciousness in its highest phase, I mean reason. Reason is the faculty of supreme comprehension, the idea of totality. How reason manifests itself in the theoretical sphere Kant has shown, and it does the same in the practical: it makes us capable of observing and surveying the whole of our life, thought, and action, in continual connection, and therefore of acting according to general maxims, whether those maxims originate in the understanding as prudential rules, or in the better consciousness as moral laws.
[Footnote 1: Epistles, 56.]
If any desire or passion is aroused in us, we, and in the same way the lower animals, are for the moment filled with this desire; we are all anger, all lust, all fear; and in such moments neither the better consciousness can speak, nor the understanding consider the consequences. But in our case reason allows us even at that moment to see our actions and our life as an unbroken chain,—a chain which connects our earlier resolutions, or, it may be, the future consequences of our action, with the moment of passion which now fills our whole consciousness. It shows us the identity of our person, even when that person is exposed to influences of the most varied kind, and thereby we are enabled to act according to maxims. The lower animal is wanting in this faculty; the passion which seizes it completely dominates it, and can be checked only by another passion—anger, for instance, or lust, by fear; even though the vision that terrifies does not appeal to the senses, but is present in the animal only as a dim memory and imagination. Men, therefore, may be called irrational, if, like the lower animals, they allow themselves to be determined by the moment.
So far, however, is reason from being the source of morality that it is reason alone which makes us capable of being rascals, which the lower animals cannot be. It is reason which enables us to form an evil resolution and to keep it when the provocation to evil is removed; it enables us, for example, to nurse vengeance. Although at the moment that we have an opportunity of fulfilling our resolution the better consciousness may manifest itself as love or charity, it is by force of reason, in pursuance of some evil maxim, that we act against it. Thus Goethe says that a man may use his reason only for the purpose of being more bestial than any beast:
Um theirischer als jedes Thier zu sein.
For not only do we, like the beasts, satisfy the desires of the moment, but we refine upon them and stimulate them in order to prepare the desire for the satisfaction.
Whenever we think that we perceive a trace of reason in the lower animals, it fills us with surprise. Now our surprise is not excited by the good and affectionate disposition which some of them exhibit—we recognise that as something other than reason—but by some action in them which seems to be determined not by the impression of the moment, but by a resolution previously made and kept. Elephants, for instance, are reported to have taken premeditated revenge for insults long after they were suffered; lions, to have requited benefits on an opportunity tardily offered. The truth of such stories has, however, no bearing at all on the question, What do we mean by reason? But they enable us to decide whether in the lower animals there is any trace of anything that we can call reason.
Kant not only declares that all our moral sentiments originate in reason, but he lays down that reason, in my sense of the word, is a condition of moral action; as he holds that for an action to be virtuous and meritorious it must be done in accordance with maxims, and not spring from a resolve taken under some momentary impression. But in both contentions he is wrong. If I resolve to take vengeance on some one, and when an opportunity offers, the better consciousness in the form of love and humanity speaks its word, and I am influenced by it rather than by my evil resolution, this is a virtuous act, for it is a manifestation of the better consciousness. It is possible to conceive of a very virtuous man in whom the better consciousness is so continuously active that it is never silent, and never allows his passions to get a complete hold of him. By such consciousness he is subject to a direct control, instead of being guided indirectly, through the medium of reason, by means of maxims and moral principles. That is why a man may have weak reasoning powers and a weak understanding and yet have a high sense of morality and be eminently good; for the most important element in a man depends as little on intellectual as it does on physical strength. Jesus says, Blessed are the poor in spirit. And Jacob Böhme has the excellent and noble observation: Whoso lies quietly in his own will, like a child in the womb, and lets himself be led and guided by that inner principle from which he is sprung, is the noblest and richest on earth. 
[Footnote 1: Epistles, 37.]