We know Socrates, who left no writings, only through the accounts of his disciples, Plato and Xenophon, and through second-hand pieces of information. But everything that seems unclear to us, debatable and incomplete in Socrates' doctrine can be completed and clarified from Spinoza's works. It would not be exaggerated, I think, to say that Socrates was resurrected in Spinoza or even that Spinoza was the second incarnation of Socrates. "Let us sacrifice with reverence to the shade of the holy, rejected Spinoza," says Schleiermacher, who was, according to Dilthey, the greatest of the German theologians after Luther. It was in the same tone the ancients spoke of Socrates — the best of men, the righteous one, the holy one. If recourse could be had to the oracle in modern times, it would certainly have called Spinoza, as it once did Socrates, the wisest of men.
Kierkegaard reproaches philosophers for not living in accordance with the categories in which they think. This reproach perhaps contains some truth, but it is certainly not applicable either to Socrates or to Spinoza. What makes both of them so remarkable is precisely the fact that they did live in the categories in which they thought, thus miraculously transforming the "true philosophy" into the "best philosophy," to use Spinoza's terms, or incarnating knowledge in virtue, to speak as Socrates did. In Socrates, universal and necessary truth led to the "highest good"; in Spinoza, his tertium genus cognitionis, cognitio intuitiva (third kind of knowledge, intuitive knowledge), ended in the amor Dei intellectualis (intellectual love of God) and the supreme beatitudo (blessedness) that is connected with it. But it is an error to brush aside, as people too often do, the fundamental idea of Socrates and Spinoza by invoking their "intellectualism." One can thus rid himself of them, but it is then impossible to understand the problem on which the thought of the wisest among men, both in his first and second incarnations, was entirely concentrated. To this the subsequent development of philosophy clearly bears witness. "All knowledge starts with experience" — so begins the Critique of Pure Reason; but Kant adds immediately that it does not follow from this that it comes entirely from experience. And, indeed, there is in our knowledge something that we never find in experience, a certain Zutat (seasoning) according to Hegel's expression, or, to speak as Leibniz did, "there is nothing in the intellect that was not in the senses, except the intellect itself." Our knowledge reduces itself entirely to this mysterious Zutat, and in the end experience plays hardly any role in the act of knowing.
It is true that those who sought knowledge were always interested in not detaching it from experience and also often substituted experience for knowledge. Scarcely had Aristotle said "all men desire by nature to know"  than he hastened to add: "this is seen in the pleasure that sensible perception gives us." But Aristotle knew perfectly well that knowledge is distinguished toto coelo from sensible perception. We recall with what insistence he emphasized that knowledge is knowledge of the universal and the necessary and that it is such knowledge alone that science seeks. We ought then to say: knowledge begins with experience and ends by completely brushing it aside. There is not, there must not be, any place in science for "pleasure in sensible perception." The purpose of knowledge is to detach itself from the sensible given, to overcome it. The sensible given is something that arises and disappears continually and never abides, something that one cannot take hold of and must consequently rid himself of, or, as the philosophers say, that one must raise himself above.
This is what Socrates taught; and such was also the meaning of Spinoza's philosophic "conversion." The unstable and transitory character of everything terrestrial filled his soul with disquietude and anxiety, as he himself admits in his Tractatus de intellectus emendatione. The attachment to the sensible given which, as Aristotle rightly remarked, is proper to all men, and which Spinoza also experienced, constitutes at first blush a very natural human aptitude, but in reality it is laden with threats and prepares for us the worst catastrophes. How can one attach himself to that which has a beginning and must, consequently, have an end? How can one admit such a dependence? The more passionately we attach ourselves to the temporal, to the passing, the more grievous will be the pain of parting when the moment comes for the object of our attachment to return into that nothingness from whence it arose for a brief moment. Even though pleasure in sensible perception be proper to all men, it does not constitute a common virtue, a principle of power, but rather a common defect, a principle of weakness. And if Aristotle approximated it to knowledge, this was only thanks to a misunderstanding, perhaps intentional. Aristotle took his departure from Socrates and Plato and, as we know, always emphasized that knowledge is of the universal and that if everything were reduced to sensible perceptions (ta aisthêta) there would be no knowledge. Knowledge thus presupposes a certain transformation of man: he denies what he loved, what he was attached to, and devotes himself to something quite new that differs entirely from the object of his former attachment.
Even though he despised the Bible and so never took the trouble to reflect on the philosophic import of the myth of the fall, Hegel saw correctly when he said that the fruit of the tree of knowledge is what in modern language is called reason, which draws everything out of itself and which since Socrates has become the principle of philosophy for all time. But Hegel could never decide to draw from this idea the conclusions that follow from it and to say, as did Spinoza: "We may therefore conclude absolutely that Scripture must neither be accommodated to reason nor reason to Scripture."  Just like Aristotle, Hegel possessed a safety valve in case the tension should become too dangerous. That is why, like Aristotle, he did not discern the bull of Phalaris hidden behind the wisdom of Socrates. That is also why he did not suspect that the words of the God of the Bible could be true, that is to say, that knowledge would poison the joy of existence and lead man, through terrible and loathsome trials, to the threshold of nothingness. Why did Aristotle and Hegel remain blind to what Socrates and Spinoza saw? I do not know. But everything leads me to believe that neither Aristotle nor Hegel learned anything from the Socratic-Spinozist vision.
From the pieces of information we possess it is difficult to determine how Socrates resolved the problem of free will. But Spinoza knew that men were as little free as inanimate objects. Had the stone been endowed with consciousness it would imagine that it falls freely (se liberrimum esse). In the same letter (LVIII) Spinoza further says: "Without, I hope, contradicting my consciousness, that is, my reason and experience, and without cherishing ignorance and misconception, I deny that I can by any absolute power of thought think that I wish or do not wish to write." And immediately afterwards, to remove all doubt from the reader, he explains: "I appeal to the consciousness, which he has doubtless experienced, that in dreams he has not the power of thinking that he wishes or does not wish to write; and that, when he dreams that he wishes to write, he has not the power not to dream that he wishes to write."
How are we to understand these puzzling words? It would seem less proper for the clear-headed Spinoza than for anyone else to seek in dreams the explanation of what happens in reality. No one denies that sleep fetters the human will. But sleep is followed by awakening, which consists precisely in the fact that man breaks the fetters which paralyze his will. It often happens to us, even before we awaken, to feel that everything that is occurring belongs not to true reality but to dream-reality, which, at the cost of a certain effort, we can brush aside and cast away from ourselves. To be sure, if the sleeper had preserved that capacity for clear and contradiction-free thought, of which Spinoza and his teacher Descartes speak so much to us, he would have to say that his judgment that he is sleeping and that his reality is a dream -reality conceals within itself a contradiction and must therefore be considered false: it is in the dream-state, indeed, that it seems to him that he is sleeping and dreaming. Besides, the sleeper, like the awakened person, does not feel himself, generally speaking, bound or deprived in any sense of his liberty; in dreaming we no more feel ourselves in the power of a strange force than in the state of waking. A suspicion penetrates into us only when we begin to feel that the force which dominates us is hostile to us, when the dream becomes a nightmare. It is then only that there suddenly comes to our minds the absurd, inept idea - one recognizes the absurd, the inept, by the fact that it contains an inner contradiction — that this reality is not the true reality but a dream, a lie, an illusion.
At the same time we suddenly find ourselves before a dilemma: what shall we choose — the reality of the nightmare or the absurd assumption? The reality of the nightmare offends our entire being; to admit the absurd is an offense against reason. It is impossible not to choose, for if one does not himself decide, someone or something will decide for him. In dreaming, as is known, man chooses the absurd assumption: before the horror of the nightmare the fear of offending reason loses all power over us — we awaken. In the state of waking a different "order" prevails. We "accept" everything — no matter how shameful, how repugnant, how frightening that which we must accept appears — provided only that reason, as well as the principle of contradiction which protects it, be not outraged. For, Quam aram parabit sibi qui majestatem rationis laedit? (What altar will he build for himself who insults the majesty of reason?), as Spinoza, who denied the freedom of man, wrote.
Or was Nicolas of Cusa closer to the truth in affirming that God lives "inside the wall of the coincidence of opposites" and that this wall "is guarded by an angel stationed at the entrance to Paradise"? It is true that it is obviously not given man to drive this angel away; and besides, not only Spinoza, who did not believe, but still more the believer will shudder with horror at the idea that he should raise his hand against the guardian posted by God Himself at the gate of Paradise. For what altar will the man who violates the commandment of God build for himself? There cannot even be a question, it seems, of "free" decision here. To pass from the nightmarish dream to the beneficent reality of the waking state is not forbidden to man, but to pass from the nightmare of reality to the God who lives inside the wall of contradiction — this is not given to us; God Himself here sets a bound to our freedom.
Spinoza, of course, would not have admitted the formula of Nicolas of Cusa; for Spinoza, the God of Nicolas of Cusa, his paradise, his angel stationed at the entrance to Paradise — all these were only the images of a naïve mind which still had not freed itself from traditions and prejudices. But the thought of Nicolas of Cusa expresses the pathos of the Spinozist philosophy more completely than Spinoza's own words — quam aram parabit sibi. And further, quam aram parabit sibi is also an image in which can be found traces of that very tradition which had inspired Nicolas of Cusa with the idea of the angel posted at the door of Paradise. But the chief thing is that both Nicolas of Cusa and Spinoza were firmly "convinced" that it is not given mortal men to overcome the bounds established by the "law" of contradiction and that, consequently, one cannot escape the nightmare of reality. The philosopher is obliged, like everyone else, to accept reality; before reality the philosopher finds himself as impotent as anyone. The only thing then that the philosopher can and must do is to teach men how they should live in the midst of this nightmarish reality from which one cannot awaken because it is the only reality. What this means is that the aim of philosophy is not truth but edification, or, to put it differently, not the fruits of the tree of life but the fruits of the tree of knowledge. It is thus that Socrates understood the task of philosophy in antiquity, and it is thus that Spinoza understood it in modern times.
We have already heard Socrates. Let us now listen to Spinoza who completed what Socrates had begun. Spinoza's task consisted in uprooting from the human soul the ancient idea of God. As long as this persists in man, we live not in the light of truth but in the darkness of falsehood. All prejudices, writes Spinoza, "spring from the notion, commonly entertained, that all things in nature act as men themselves act, namely, with an end in view. It is accepted as certain that God Himself directs all things to a definite end, for it is said that God made all things for man, and man that he might worship Him."  All prejudices have for their source the conviction that God sets up purposes or goals. Now in reality, "God... has no principle or goal of action." 
When one reads this, one asks himself before everything else: "Is Spinoza right or not? Do the people who believe that God sets Himself certain purposes know the truth, while those who affirm that every purpose is alien to God deceive themselves? Or is the contrary the case?" Such is the first question that arises quite naturally, or of itself, before us. But given what Spinoza has previously said to us, we must raise another question before this one: "Is man free to choose this or that answer when it is a question of knowing whether God does or does not set Himself purposes? Or is the answer to this question already prepared in advance, before man poses the question, before man who asks it has even risen from nothingness into being?" We recall that Spinoza has openly admitted to us that he was not free to write or not to write. Is he then free to choose between this or that solution to the question that presented itself to him? A hundred years later Kant fell into the same snare. Metaphysics, he says, must decide whether God exists, whether the soul is immortal, whether the will is free. But if the will is not free or if its freedom is doubtful, then it is not given man to choose when it is a question of God's existence and the soul's immortality. Someone or something has already decided, without him, the question of God's existence and the soul's immortality; whether he wishes it or not, he is obliged to accept the answer that will be presented to him.
 Metaphysics, 980a, 21.
 Tract. Theol.-Polit., XV, 19 f.
 Ethics I, App.
 Ethics IV, Praef.