Our knowledge springs from two fundamental sources of our mind; the first is to receive representations (receptivity of impressions), the second is the faculty of knowing an object through these representations (spontaneity of concepts). Through the first an object is *given* to us, through the second the object is *thought* in relation to that representation (which is a mere determination of the mind). Intuition and concepts constitute, therefore, the elements of all our knowledge, so that neither concepts without an intuition in some way corresponding to them, nor intuition without concepts can yield knowledge. Both are either pure or empirical. They are empirical when they contain sensation (sensation presupposes the actual presence of the object). They are *pure* when no sensation is mixed in with the representation. Sensation may be called the matter of sensible knowledge. Pure intuition, therefore, contains only the form under which something is intuited, and the pure concepts contains only the form of thinking an object in general. Pure intuitions and pure concepts alone are possible *a priori*, empirical intuitions and empirical concepts only *a posteriori*. We call *sensibility* the *receptivity* of our mind to receive representations insofar as it is in some wise affected, while the *understanding*, on the other hand, is our faculty of producing representations by ourselves, or the *spontaneity* of knowledge. We are so constituted that our intuition can never be other than *sensible*; that is, it contains only the mode in which we are affected by objects. The faculty, on the contrary, which enables us to *think* the object of sensible intuition is the *understanding*. Neither of these properties is to be preferred to the other. Without sensibility no object would be given to us, without understanding no object would be thought. Thoughts without content are empty, intuitions without concepts are blind. It is, therefore, just as necessary to make our concepts sensible (i.e., to add the object to them in intuition) as to make our intuitions understandable (i.e., to bring them under concepts). These two faculties or capacities cannot exchange their functions. The understanding cannot intuit anything, the senses cannot think anything. Only from their union can knowledge arise. But this is no reason for confounding their respective contributions; rather, it gives us a strong reason for carefully separating and distinguishing the one from the other. We therefore distinguish the science of the rules of sensibility in general, i.e., aesthetic, from the science of the rules of the understanding in general, i.e., logic."―Transcendental Doctrine of Elements. Transcendental Logic: The Idea of a Transcendental Logic
After this manner conceive that a flatterer differs from a friend: for it often happens to both that they engage in the same employments and the same associations; but the one differs from the other in use, in the end, and in the disposition of the soul: for the friend considers that which appears to him to be good to belong also in common to his friend; and, whether this proves to be painful or pleasant, he partakes equally of it with him; but the flatterer, following his own desires, conducts the association to his own advantage. The friend desires an equality of good, the flatterer his own private good. The one aspires after equal honour in virtue, the other after superiority in pleasure. The one in conversation desires an equal freedom of speech, the other servile submission. The one loves truth in association, the other deception; and the one looks to future emolument, but the other to present delight. The one requires to be reminded of his good actions, the other wishes them to be involved in oblivion. The one takes care of the possessions of his friend, as of things common, the other destroys them, as being the property of another. The company of a friend in prosperity is most opportune, and in calamity is most equal; but a flatterer can never be satiated with prosperity, and in adversity he is never to be seen. Friendship is laudable, flattery detestable; for friendship attends to equality of retribution, but this flattery mutilates: for he who pays servile attention to another through indigence, that his wants may be supplied, so far as he does not receive an equal submission in return, will reprobate the inequality. A friend, when his friendship is concealed, is unhappy; on the contrary, a flatterer is miserable when is flattery is not concealed. Friendship when tried is strengthened, flattery is confuted, by time. Friendship requires not to be corroborated by advantage, but flattery cannot subsist without profit; and if men have any communion with the divinities, the pious man is a friend to divinity, but the superstitious is a flatterer of divinity; and the pious man is blessed, but the superstitious is miserable.