A man shouldn’t claim to know even himself as he really is by knowing himself through inner sensation — i.e. by introspection. For since he doesn’t produce himself (so to speak) or get his concept of himself a priori but only empirically, it is natural that he gets his knowledge of himself through inner sense and consequently only through how his nature appears and how his consciousness is affected. But beyond the character of his own subject, which is made up out of these mere appearances, he necessarily assumes something else underlying it, namely his I as it is in itself. Thus in respect to mere perception and receptivity to sensations he must count himself as belonging to the sensible world; but in respect to whatever pure activity there may be in himself (which reaches his consciousness directly and not by affecting the inner or outer senses) he must count himself as belonging to the intellectual world — though he doesn’t know anything more about it.

Man is conscious of a universal soul within or behind his individual life, wherein, as in a firmament, the natures of Justice, Truth, Love, Freedom, arise and shine. This universal soul, he calls Reason: it is not mine, or thine, or his, but we are its; we are its property and men. And the blue sky in which the private earth is buried, the sky with its eternal calm, and full of everlasting orbs, is the type of Reason. That which, intellectually considered, we call Reason, considered in relation to nature, we call Spirit. Spirit is the Creator. Spirit hath life in itself. And man in all ages and countries, embodies it in his language, as the FATHER.

How can man know himself? It is a dark, mysterious business: if a hare has seven skins, a man may skin himself seventy times seven times without being able to say, “Now that is truly you; that is no longer your outside.” It is also an agonizing, hazardous undertaking thus to dig into oneself, to climb down toughly and directly into the tunnels of one’s being. How easy it is thereby to give oneself such injuries as no doctor can heal. Moreover, why should it even be necessary given that everything bears witness to our being — our friendships and animosities, our glances and handshakes, our memories and all that we forget, our books as well as our pens. For the most important inquiry, however, there is a method. Let the young soul survey its own life with a view of the following question: “What have you truly loved thus far? What has ever uplifted your soul, what has dominated and delighted it at the same time?” Assemble these revered objects in a row before you and perhaps they will reveal a law by their nature and their order: the fundamental law of your very self. Compare these objects, see how they complement, enlarge, outdo, transfigure one another; how they form a ladder on whose steps you have been climbing up to yourself so far; for your true self does not lie buried deep within you, but rather rises immeasurably high above you, or at least above what you commonly take to be your I.

Reason is man’s faculty for grasping the world by thought, in contradiction to intelligence, which is man’s ability to manipulate the world with the help of thought. Reason is man’s instrument for arriving at the truth, intelligence is man’s instrument for manipulating the world more successfully; the former is essentially human, the latter belongs to the animal part of man.

he who knows himself is intelligent.

It is reason which breeds pride and reflection which fortifies it; reason which turns man inward into himself; reason which separates him from everything which troubles or affects him. It is philosophy which isolates a man, and prompts him to say in secret at the sight of another suffering: 'Perish if you will; I am safe.' No longer can anything but dangers to society in general disturb the tranquil sleep of the philosopher or drag him from his bed. A fellow-man may with impunity be murdered under his window, for the philosopher has only to put his hands over his ears and argue a little with himself to prevent nature, which rebels inside him, from making him identify himself with the victim of the murder. The savage man entirely lacks this admirable talent, and for want of wisdom and reason he always responds recklessly to the first promptings of human feeling.

Human reason reduced to its own resources is perfectly worthless, not only for creating but also for preserving any political or religious association, because it only produces disputes, and, to conduct himself well, man needs not problems but beliefs. His cradle should be surrounded by dogmas, and when his reason is awakened, it should find all his opinions ready-made, at least all those relating to his conduct. Nothing is so important to him as prejudices.

The universe our reason conceives is, in fact, a universe which extends infinitely beyond human experience, the characteristic of reason being to prolong the data of experience, to extend them by way of generalization, in order to make us conceive many more things than we shall ever perceive. In such a universe man is expected to do very little and to occupy very little space: what he gives to his intelligence he takes away from his will. Above all, having attributed to his thought the power of embracing everything, he is obliged to imagine all things in terms of thought; of his aspirations, his desires, his enthusiasms he cannot ask enlightenment in a world in which everything accessible to him has been first considered by him as translatable into pure ideas. His sensibility cannot enlighten his intelligence, for it is with his intelligence that he has made what light there is. Most philosophies, therefore, restrict our experience on the side of feeling and will as at the same time they indefinitely prolong it on the side of thought.

For my part, when I enter most intimately into what I call myself, I always stumble on some particular perception or other, of heat or cold, light or shade, love or hatred, pain or pleasure. I never can catch myself at any time without a perception, and never can observe any thing but the perception…. If any one, upon serious and unprejudic'd reflection thinks he has a different notion of himself, I must confess I can reason no longer with him. All I can allow him is, that he may be in the right as well as I, and that we are essentially different in this particular. He may, perhaps, perceive something simple and continu'd, which he calls himself; tho' I am certain there is no such principle in me.

Because reason...is the only thing that makes us men, and distinguishes us from the beasts, I would prefer to believe that it exists, in its entirety, in each of us...

When Spinoza in the seventeenth century used the word reason, he meant an attitude toward life in which the mind united the emotions with the ethical goals and other aspects of the “whole man.” When people today use the term they almost always imply a splitting of the personality. They ask in one form or another: “Should I follow reason or give way to sensual passions and needs or be faithful to my ethical duty?

Since everything that comes into the human mind enters through the gates of sense, man's first reason is a reason of sense-experience. It is this that serves as a foundation for the reason of the intelligence; our first teachers in natural philosophy are our feet, hands, and eyes. To substitute books for them does not teach us to reason, it teaches us to use the reason of others rather than our own; it teaches us to believe much and know little.

After man has persuaded himself that all things which exist are made for him, he must in everything adjudge that to be of the greatest importance which is most useful to him, and he must esteem that to be of surpassing worth by which he is most beneficially affected. In this way he is compelled to form those notions by which he explains nature; such, for instance, as good, evil, order, confusion, heat, cold, beauty, and deformity, etc.; and because he supposes himself to be free, notions like those of praise and blame, sin and merit, have arisen.

A person of any mental quality has ideas of his own. This is common sense.