Thus we need no metaphysics, or if we are to allow any at all, then only one which understands how to live in good understanding with science, and even to subordinate itself to it. For - this we can predict with assurance - if it should come to a conflict between metaphysics and science, the former would be "swept off the face of the earth". Modern philosophy has grown to stature and strength in consciousness of this. Since Descartes, and particularly since Spinoza, no recognized philosopher has been able to speak or think otherwise.
Spinoza left us as his heritage an "ethica, ordine geometrica demonstrata". No one doubts that Spinoza's system is a metaphysical one. But many people are convinced that Spinoza was still unacquainted with the "criticism" created by Kant. In the textbooks of philosophy this is often represented as though Spinoza, had he lived after Kant, could no longer have said what he did say. But this can hardly be correct. Clearly all the essential part of Kant's criticism was already contained fully and completely in Spinoza's more geometrico. Like Kant, Spinoza wanted no "arbitrary" metaphysics. He aimed at the strictly scientific, and if he clothed his thoughts in the form of mathematical conclusions, he did so precisely because he, like Kant after him, was chiefly concerned with putting an end, once and for all, to the capricious multifariousness of opinions and creating a permanent uniformity of judgments, bound up with the idea of necessity. The axioms, postulates, and theorems - all these wrappings which are unaccustomed and apparently useless to the reader of philosophic books, in which Spinoza clothed his truths, did their service. Even as a servant once reminded the King of the Persians of the Athenians, so they reminded Spinoza that metaphysics may contain no arbitrariness, but must be strict science.
Incidentally, Spinoza, like many other great philosophers, gives no exact answer to the question, What is science? Even Kant, when he wrote the Critique of Pure Reason, gave no exhaustive answer to this question. What is science? Every one knows this: geometry, arithmetic, astronomy, physics, even history. But no one goes beyond examples and commonplaces. Even a correct definition of reason is nowhere to be found - not even in the same Kant who wrote the Critique of Pure Reason. It is assumed that every one knows what reason is, as they also know what science is. But if we try to gather from the works of the philosophers an idea of what reason and science are, everything comes just to this: reason and science give us judgments of universal validity. And where, by this path or that, we attain to universally valid judgments, all doubts and arguments have an end and must have an end; there every one has always thought alike and will always think alike, and there, consequently, lies eternal truth.
For this reason philosophers, from antiquity down to the present day, have kept their eyes on mathematics. Plato eschewed the company of men who had no knowledge of geometry, Kant called mathematics a "royal science", and even Spinoza, honest Spinoza, thought it his duty to make it appear to himself that that truth after which he sought with such agony was in its nature no different from mathematical truth. When one of his correspondents asked him by what right he held his philosophy to be the best, he answered that he did not at all hold it for the best, but for the true philosophy, and that for the same reason by virtue of which every one believes that the sum of the angles of a triangle is equal to two right angles.
Thus Spinoza answered his irate correspondent, so he spoke in his works on every occasion, and sometimes, indeed, without occasion. In the Ethics he promises to treat of God, the understanding, and the human passions as though speaking of planes and triangles, and swears a solemn oath to eliminate from his philosophic vocabulary all words which recall, however faintly, human wishes, human seeking and struggling. Neither the good nor the evil, neither the beautiful nor the ugly shall, he says, influence his method of seeking the truth. Man is a member, or one of the infinitely numerous members, in the uniform, infinite whole which he called, now God, now Nature, now Substance. The task of philosophy amounted to this: to "understanding" the complicated and ingenious mechanism by which the infinite number of individual parts are fused into a uniform and self-sufficient whole. He did not abolish the word "God", and even in the same letter to his irate correspondent emphasizes that his philosophy allows God the same place of honour as other systems grant him: honest Spinoza did not shrink even from this lie.
I draw very especial attention to this circumstance, for since the days of Spinoza, who took on himself the whole burden of responsibility for that lie which has only achieved fame in the history of modern days, this kind of distortion has been exalted almost into a philosophical virtue. It should be clear even to the blind that the equation, God = nature = substance, ought to mean that we need not and must not allow God any further place in philosophy. In other words, if we are seeking the last truth, we must turn to the same place whither the mathematicians turn when solving their problems. If we ask ourselves what is the sum of the angles of a triangle, do we expect that he who gives us the answer to our question shall be free to answer it in this way or in that, i.e. that he possesses an attribute by which we distinguish a living being from a not-living, an animate from an inanimate?
What gives mathematics its distinction of exactitude and certainty which are so seductive for us, and, in connection therewith, the universal validity and binding character of its judgments, is precisely the fact that it has renounced all human attributes, that it refuses either ridere, or lugere, or detestari, because it needs only what Spinoza describes by the word intelligere. And if philosophy claims for itself the same certainty and universal validity, it has no other recourse. It must strive only for intelligere, and eschew as non-existent and illusory everything which does not fit into the framework of intelligere. But we know already what Spinoza's intelligere means. It means conceiving the world as an infinitely great number of parts (Leibniz afterwards used the term "monads"), which move according to eternally existent laws and have neither the ability nor the right to alter by a hair's breadth the order which was set up without them, and not at all for their benefit. And in this respect God differs in no way from man. His "freedom", too, consists only in submission to an order which is again only the expression of His being. Deus ex solis suae naturae legibus et a nemine coactus agit - God acts only in accordance with the laws of His own nature, and none compels Him.
Therefore, even in his "theological-political treatise", Spinoza raises the question of the meaning and significance of the Bible, and decides it without any visible hesitation. In the Bible, he says, there is no truth, nor is the Bible the place for truths. It contains only moral lessons. These we might take from the Bible, but the truth we must seek elsewhere. Nor does the Bible lay any claim to truth, and that which is retailed in it does not look in the least like truth. God did not create the world in six days. God never blessed mankind, did not reveal Himself to Moses on Mount Sinai, did not lead the Jews out of Egypt, etc. All these things are only poetic images, i.e. inventions which a sensible man interprets in a relative and limited sense. Moreover, that God of whom the Bible tells so much does not exist and never has existed - this again is testified by reason, by that something which solves irrevocably mathematical problems and teaches man to distinguish truth from lies in mathematics. And finally - this was perhaps of quite especial importance and significance for the future - not only does that God of whom the Bible tells not exist, but there is not even any necessity for such a God. For man - such again is the decree of that reason which acknowledges no power above itself thanks to which we know that the sum of the angles of a triangle is equal to two right angles - for man, the essential point is not whether there is a God, but whether men can retain the full piety to which the peoples, educated in Holy Writ, have grown accustomed in the course of the centuries. Spinoza, who believed in the infallibility of reason, submitted without a murmur also to this decision of reason. Yes, we can and must reject God - but we can and must retain piety and religious feeling. But if this is so, then the conceptions of "substance" or "nature", which do not hurt the understanding of a man trained in mathematics, can excellently well replace the idea of God become unacceptable to all men.
Spinoza's formula, "Deus = natura = substantia", like all the conclusions drawn from it in his Ethics and his earlier works, simply means that there is no God. This discovery of Spinoza's became the starting-point for modern philosophical thought. However much one may talk of God, yet we know with certainty that we are not speaking of that God who once lived in Biblical days, who created Heaven and earth and man after His image, who both loves and also desires, is excited and repentant, strives with man and even sometimes gets the worst of it in that strife. Reason, the same reason which rules over triangles and perpendiculars and which, therefore, thinks that it owns the sovereign right to distinguish truth from lies; reason which seeks, not for the best but the true philosophy - this reason declares with the self-sufficiency peculiar to itself, in a tone which admits no contradiction, that such a God can be no supremely perfect being, not even a perfect being at all, and can consequently be no God. The fate of Thales inevitably awaits any man who refuses to accept reason's decision: he will fall into the well, and all earthly joys will be unattainable for him.