Spinoza was a lens crafter by trade, an exciting engineering field at the time because of great discoveries being made by telescopes. The full impact of his work only took effect sometime after his death and after the publication of his Opera Posthuma. He is now seen as having prepared the way for the 18th century Enlightenment, and as a founder of modern biblical criticism.

Life
Born to a great family of Sephardic Jews, among the Portuguese Jews of Amsterdam, he gained fame for his positions of pantheism and neutral monism, as well as the fact that his Ethics was written in the form of postulates and definitions, as though it were a geometry treatise. In the summer of 1656, he was excommunicated because of apostasy from the Jewish community for his claims that God is the mechanism of nature and the universe, having no personality, and that the Bible is a metaphorical and allegorical work used to teach the nature of God, both of which were based on a form of Cartesianism (see René Descartes). Following his excommunication, he adopted the first name Benedictus (the Latin equivalent of his given name, Baruch). The terms of his excommunication were quite severe; see Kasher and Biderman (19nn).

After his excommunication, he lived and worked for a while in the school of Franciscus van den Enden, who taught him Latin and may have introduced him to modern philosophy. In this period Spinoza also became acquainted with several Collegiants, members of a non-dogmatic and interdenominational sect with tendencies towards Rationalism. By the beginning of the 1660s Spinoza's name became more widely known, and eventually Leibniz and Henry Oldenburg paid him visits.

He corresponded with the latter for the rest of his life. Spinoza's first publication was his Principles of Cartesian Philosophy, a work that introduced some of his own ideas. In 1665 he notified Oldenburg that he had started to work on a new book, the Theologico-Political Treatise, published in 1670.

Since the public reactions to the anonymously published Theologico-Political Treatise turned unfavourable to his brand of Cartesianism, Spinoza abstained from publishing more of his works. Wary and independent, he wore a signet ring engraved with his initials, a rose and the word "caute" (Latin for caution). The Ethics and all other works, apart from the Principles of Cartesian Philosophy and the Theologico-Political Treatise, were published after his death in the Opera Postuma edited by his friends.

Philosophy - Overview
Known as both the "greatest Jew" and the "greatest Atheist", Spinoza contended that God and Nature were two names for the same reality, namely the single substance (meaning "to stand beneath" rather than "matter") that underlies the universe and of which all lesser "entities" are actually modes or modifications. The argument for this single substance runs something as follows:

1. Substance exists and cannot be dependent on anything else for its existence.
2. No two substances can share an attribute.
Proof: If they share an attribute, they would be identical. Therefore they can only be individuated by their modes. But then they would depend on their modes for their identity. This would have the substance being dependent on its mode, in violation of premise 1. Therefore, two substances cannot share the same attribute.
3. A substance can only be caused by something similar to itself (something that shares its attribute).
4. Substance cannot be caused.
Proof: Something can only be caused by something which is similar to itself, in other words something that shares its attribute. But according to premise 2, no two substances can share an attribute. Therefore substance cannot be caused.
5. Substance is infinite.
Proof: If substance were not infinite, it would be finite and limited by something. But to be limited by something is to be dependent on it. However, substance cannot be dependent on anything else (premise 1), therefore substance is infinite.

Conclusion: There can only be one substance.
Proof: If there were two infinite substances, they would limit each other. But this would act as a restraint, and they would be dependent on each other. But they cannot be dependent on each other (premise 1), therefore there cannot be two substances.

Spinoza contended that "Deus sive Natura" ("God or Nature") was a being of infinitely many attributes, of which extension and thought were two. His account of the nature of reality, then, seems to treat the physical and mental worlds as two different, parallel "subworlds" that neither overlap nor interact. This formulation is a historically significant panpsychist solution to the mind-body problem known as neutral monism.

Spinoza was a thoroughgoing determinist who held that absolutely everything that happens occurs through the operation of necessity. For him, even human behaviour is fully determined, freedom being our capacity to know we are determined and to understand why we act as we do. So freedom is not the possibility to say "no" to what happens to us but the possibility to say "yes" and fully understand why things should necessarily happen that way.

By forming more "adequate" ideas about what we do and our emotions or affections, we become the adequate cause of our effects (internal or external), which entails an increase in activity (versus passivity). This means that we become both more free and more like God, as Spinoza argues in the Scholium to Prop. 49, Part II.
Spinoza's philosophy has much in common with Stoicism in as much as both philosophies sought to fulfil a therapeutic role by instructing people how to attain happiness (or eudaimonia, for the Stoics). However, Spinoza differed sharply from the Stoics in one important respect: he utterly rejected their contention that reason could defeat emotion. On the contrary, he contended, an emotion can be displaced or overcome only by a stronger emotion.

For him, the crucial distinction was between active and passive emotions, the former being those that are rationally understood and the latter those that are not. He also held that knowledge of true causes of passive emotion can transform it to an active emotion, thus anticipating one of the key ideas of Sigmund Freud's psychoanalysis.

Some of Spinoza's philosophical positions are:

1. God is the natural world and has no personality.
2. The natural world is infinite.
3. There is no real difference between good and evil.
4. Everything must necessarily happen the way that it does. Therefore, there is no free will.
5. Everything done by humans and other animals is excellent and divine.
6. All rights are derived from the State.
7. Animals can be used in any way by people for the benefit of the human race.

Philosophy - Ethics
Encapsulated at the start in his Treatise on the Improvement of the Understanding (Tractatus de intellectus emendatione) is the core of Spinoza's ethical philosophy, what he held to be the true and final good. Spinoza held a relativist's position, that nothing is good or bad, except to the extent that it is subjectively perceived to be by the individual.

For instance, one person may find roasted peanuts tasty and so for her roasted peanuts are good. But another person may be allergic to nuts and so for him peanuts are bad. Spinoza's point is, there is nothing inherent in any thing, like a nut, to make it either good or bad. From this he concluded the ethical ventures of other philosophers had been mistaken. His words put it best themselves.

"After experience had taught me that all the usual surroundings of social life are vain and futile; seeing that none of the objects of my fears contained in themselves anything either good or bad, except in so far as the mind is affected by them, I finally resolved to inquire whether there might be some real good having power to communicate itself, which would affect the mind singly, to the exclusion of all else: whether, in act, there might be anything of which the discovery and attainment would enable me to enjoy continuous, supreme, and unending happiness. I say 'I finally resolved,' for at first sight it seemed unwise willingly to lose hold on what was sure for the sake of something then uncertain. I could see the benefits which are acquired through fame and riches, and that I should be obliged to abandon the quest of such objects, if I seriously devoted myself to the search for something different and new. I perceived that if true happiness chanced to be placed in the former I should necessarily miss it; while if, on the other hand, it were not so placed, and I gave them my whole attention, I should equally fail...

"I will here only briefly state what I mean by true good, and also what is the nature of the highest good. In order that this may be rightly understood, we must bear in mind that the terms good and evil are only applied relatively, so that the same thing may be called both good and bad according to the relations in view, in the same way as it may be called perfect or imperfect. Nothing regarded in its own nature can be called perfect or imperfect; especially when we are aware that all things which come to pass, come to pass according to the eternal order and fixed laws of nature.

"However, human weakness cannot attain to this order in its own thoughts, but meanwhile man conceives a human character much more stable than his own, and sees that there is no reason why he should not himself acquire such a character. Thus he is led to seek for means which will bring him to this pitch of perfection, and calls everything which will serve as such means a true good. The chief good is that he should arrive, together with other individuals if possible, at the possession of the aforesaid character. What that character is we shall show in due time, namely, that it is the knowledge of the union existing being the mind and the whole of nature.

"This, then, is the end for which I strive, to attain to such a character myself, and to endeavour that many should attain to it with me. In other words, it is part of my happiness to lend a helping hand, that many others may understand even as I do, so that their understanding and desire may entirely agree with my own. In order to bring this about, it is necessary to understand as much of nature as will enable us to attain to the aforesaid character, and also to form a social order such as is most conducive to the attainment of this character by the greatest number with the least difficulty and danger."

The Pantheism Controversy (Pantheismusstreit)
In 1785, Friedrich Heinrich Jacobi published a condemnation of Spinoza's pantheism. Jacobi claimed that Spinoza's doctrine was pure materialism, because all Nature and God are said to be nothing but extended substance. This, for Jacobi, was the result of Enlightenment rationalism and it would finally end in absolute atheism. Moses Mendelssohn disagreed with Jacobi, saying that there is no actual difference between theism and pantheism. The entire issue became a major intellectual and religious concern for European civilization at the time.

Modern relevance
Albert Einstein said that Spinoza was the philosopher who had most influenced his worldview (Weltanschauung). Spinoza equated God (infinite substance) with Nature, and Einstein, too, believed in an impersonal deity. His desire to understand Nature through physics can be seen as contemplation of God. Arne Næss, the father of the deep ecology movement, acknowledged drawing much inspiration from the works of Spinoza.

In the late twentieth century, there was a great increase in philosophical interest in Spinoza in Europe, often from a left-wing and Marxist perspectives. Notable philosophers Gilles Deleuze, Antonio Negri and Étienne Balibar have each written books on Spinoza. Other philosophers heavily influenced by Spinoza were Constantin Brunner and John David Garcia. Stuart Hampshire wrote a major English language study of Spinoza, though H. H. Joachim's work is equally valuable.

Spinoza's portrait featured prominently on the 1000 Dutch gulden banknote, legal tender in the Netherlands until the euro was introduced in 2002.

The highest and most prestigious scientific prize of the Netherlands is named the Spinozapremie (Spinoza reward).

Quotes

"Mind and body are one and the same individual which is conceived now under the attribute of thought, and now under the attribute of extension." Ethics II prop. 7.

"I have laboured carefully, not to mock, lament, or execrate human actions, but to understand them." A Political Treatise, 288.

"If the road I have shown to lead to this is very difficult, it can yet be discovered. And clearly it must be very hard when it is so seldom found. For how could it be that it is neglected practically by all, if salvation were close at hand and could be found without difficulty? But all excellent things are as difficult as they are rare." Ethics, 224.

"Emotion, which is suffering, ceases to be suffering as soon as we form a clear and precise picture of it." Ethics