Among contemporary scholars, no one has stressed the influence and historical significance of Spinoza more than has Jonathan Israel, especially in two of his formidable books: Radical Enlightenment (Oxford, 2001) and Enlightenment Contested (Oxford, 2006). As Israel wrote in the latter volume (p. 36), although Spinoza’s infamous reputation prevented many thinkers from acknowledging their intellectual debts to him,

no one else, not even Hobbes, was denounced as often as Spinoza whether in the late seventeenth, early eighteenth, or mid eighteenth century, or in so many countries; or indeed was so widely known to the public as a universal philosophical bogeyman. In this respect, as Schmidt notes in his preface to his translation of the Ethics in 1744, Spinoza remained the most feared philosopher in eighteenth-century Europe, eclipsing in contemporary perception every other alleged “atheist” in history.

The result was spreading awareness, discussion, refutation, condemnation, and…also admiration of Spinoza often without his name being so much as mentioned.

Among the two major works by Spinoza—the Theologico-Political Treatise (1670) and the posthumously published Ethics—both of which were widely excoriated as atheistic and politically subversive—it was the Treatise that exerted the most influence on later generations of freethinkers. In the Treatise –a pioneering work in what later would be called “higher criticism” of the Bible—Spinoza insisted that we should approach the Bible as we would any other historical book (or, in this case, collection of books). We should not begin with the assumption that the Bible is divinely inspired and then afford it special treatment when we encounter stories that we would reject in any other history. Rather, we should examine biblical accounts with the same rational objectivity and critical attitude that we would apply to any other book.

As a result, Spinoza analyzed the Bible with a boldness that had rarely if ever been seen before. He provided an abundance of details to support his claim that the Bible is “faulty, mutilated, tampered with, and inconsistent.” We don’t know the authors, circumstances, or dates of many biblical books. Moreover, “we cannot say into what hands they fell, nor how the numerous varying versions originated; nor, lastly, whether there were other versions, now lost.”

Spinoza drew on various sources for his critique of the Bible. He credited Abraham ibn Ezra, a twelfth-century Rabbi, with discovering that Moses did not write all of the Pentateuch (the first five books of the Old Testament). Ezra, wrote Spinoza, “confined himself to dark hints which I shall not scruple to elucidate, thus throwing full light on the subject.” Spinoza’s “light” consisted of denying the Mosaic authorship altogether: “it is thus clearer than the sun at noonday that the Pentateuch was not written by Moses, but by someone who lived long after Moses.”

Spinoza was not the first writer of his century to question the Mosaic authorship of the Pentateuch. In Leviathan (1651), Thomas Hobbes (another notorious heretic) conceded that Moses may have written much of the Pentateuch, but he also argued that Moses “did not compile those books entirely, and in the form that we now have them.” But the pioneer of modern biblical criticism was Isaac La Peyrère, a renegade Calvinist who espoused his own peculiar brand of mysticism and messianism. Writing a decade before Hobbes, La Peyrère altogether denied the Mosaic authorship of the Pentateuch, he identified biblical inaccuracies and contradictions, he proclaimed the existence of mankind before Adam, he denied the universality of the flood, and he embraced many other heretical views. (La Peyrère later abjured—insincerely, under threat of force—over 100 such heresies.) Spinoza was familiar with La Peyrère’s ideas, and incorporated many of them in the Treatise.

Authorship of the Pentateuch may strike the modern reader as an esoteric controversy, a topic scarcely important enough to become excited or upset about, and certainly nothing that would warrant punishing anyone who denies that Moses wrote the first five books of the Bible. But this attitude, which seems commonsensical to many people today, merely illustrates how drastically things have changed over the past several centuries. In Spinoza’s day to deny the Mosaic authorship was widely regarded as a dangerous heresy, one punishable by law, because it called into question the status of the Bible as a divinely inspired document. Both orthodox Christians and their critics understood that the authenticity of a purported revelation depends on the credentials of its human messenger, or “prophet.” A miracle, if reported by a divinely inspired prophet, was deemed authentic; but that same miracle degenerated into a tall yarn if reported by an unknown and uninspired storyteller. As the deist Thomas Paine explained in The Age of Reason:

Take away from Genesis the belief that Moses was the author, on which only the strange belief that it is the word of God has stood, and there remains nothing of Genesis, but an anonymous book of stories, fable, and traditionary or invented absurdities, or downright lies.

In the Treatise, Spinoza attempted to render the Bible useless as a source of knowledge—at least for those who are able to reason philosophically. Biblical narratives, he argued, may sometimes illustrate moral precepts, such as justice and charity, but unaided reason can discover these virtues as well, without recourse to revelation (and with more certainty). So of what use is the Bible? Spinoza replied that most people lack the inclination or ability to follow a long chain of philosophic reasoning, so they must learn their morality from easily digested stories and examples. This is where the Bible plays an important role. It does not provide definitions or proof, so it cannot provide the knowledge available through reason, but the Bible’s “sayings and reasonings are adapted to the understanding of the masses.” Belief in the Bible (or certain parts of it) “is particularly necessary to the masses whose intellect is not capable of perceiving things clearly and distinctly.” In addition, ordinary people are likely to read biblical stories without grasping their moral import, so the masses “are always in need of pastors or church ministers to explain them to their feeble intelligence.”

Spinoza’s derogatory remarks about the “masses” exhibited an intellectual and moral elitism that would run throughout the history of freethought well into the eighteenth-century Enlightenment. Voltaire, for example, regarded Christian doctrines as unworthy of enlightened minds, while insisting that those selfsame doctrines were necessary to keep the unenlightened masses from running amok, morally speaking. It should be noted, however, that this attitude was not shared by all freethinkers. For example, many eighteenth-century freethinkers—such as the deists Peter Annet, Thomas Chubb, and Thomas Paine—specifically tailored their anti-Christian tracts for the common man, believing that the average person is capable of thinking for himself and arriving at rational judgments. (This became the dominant attitude of nineteenth-century freethinkers.) Government authorities typically regarded this “vulgar” popularization of freethought as a greater threat to the religious and political status quo than the more sophisticated treatments intended for academics and intellectuals. Nevertheless, when modern historians discuss the history of freethought, they almost always focus on the academic freethinkers, while dismissing what I call the “street freethinkers,” who wrote in a style that would appeal to the masses, as unworthy of serious consideration.

For Spinoza, as for many deists, the essence of a good religion is its ability to improve moral conduct. A person may believe every word of the Bible, but if this does not make him more virtuous, “he might employ himself just as profitably in reading the Koran or the poetic drama, or ordinary chronicles.” On the other hand, a person may be wholly ignorant of the Bible or  deny its divine status, but if he is a good person who leads a moral life, then “he is absolutely blessed and truly possesses in himself the spirit of Christ.” The natural light of reason, for those skilled in its use, is sufficient to show us “the true way of salvation.”

With this background, we can understand why the Theologico-Political Treatise generated a maelstrom among Spinoza’s contemporaries and for many decades thereafter. Few books have been so universally reviled. Although some theologians—Catholic, Protestant, and Jewish—invested reason with an important and independent role, they still insisted that revelation provides knowledge inaccessible and superior to reason, knowledge essential to salvation. Spinoza would have none of this. Reason, he insisted, is supreme and sufficient. If people “hawk about something superior to reason, it is mere figment, and far below reason.” Spinoza was “thoroughly convinced, that the Bible leaves reason absolutely free, that it has nothing in common with philosophy, in fact, that Revelation and Philosophy stand on totally different footings. [E]ach has its separate province, neither can be called the handmaid of the other.”

This sounds like an important concession to revelation, but, as we have seen, the “province” that Spinoza assigned to revelation is rather mundane. Obedience, not knowledge, is the “sole object” of revelation, and even here revelation is needed only when dealing with the dull-witted masses. The Bible does not presume to teach philosophy or science “but only very simple matters, such as could be understood by the slowest intelligence.”

Do reason and revelation conflict? Early in the Treatise Spinoza remarked that he found nothing “taught expressly by Scripture, which does not agree with our understanding, or which is repugnant thereto.” This apparent concession was a bit misleading, however. Later in the Treatise Spinoza stated: “I insist that [the Bible] expressly affirms and teaches that God is jealous…and I assert that such a doctrine is repugnant to reason.” After mentioning additional irrational teachings, Spinoza pushed his case even further. He asserted that the Bible contains many contradictions, thereby exposing the “absurdities” of accepting the Bible as a source of knowledge.

How are we to reconcile Spinoza’s claim that the Bible and reason are consistent with his laundry list of biblical absurdities and contradictions? Quite simply: reason gives us knowledge whereas revelation does not. Reason conflicts with revelation only if we take the Bible to be something more than a handy collection of moral lessons directed to those persons who cannot “acquire the habit of virtue under the unaided guide of reason.” The Bible is useful but not necessarily true. Reason reigns supreme in all matters of knowledge; it is “the light of the mind, and without her all things are dreams and phantoms.”

Perhaps the most scandalous part of the Theologico-Political Treatise was its unequivocal rejection of miracles. A miracle is said to be an event that contravenes the laws of nature. According to Spinoza, however, those natural laws are themselves manifestations of the divine nature, so to say that God contravened natural law is to say that God “acted against his own nature—an evident absurdity.” Indeed, since God is perceived through the “immutable order of nature,” our knowledge of God increases along with our understanding of nature. But a miracle defies rational comprehension, so it actually diminishes our knowledge of God.

In addition, a miracle would be an insult to the divine nature, because it implies that “God has created nature so weak, and has ordained for her laws so barren,” that he must repeatedly tinker with his flawed creation through miracles. Deists would later have a field day with this argument. It was even used by the German philosopher Leibniz against the claim of Isaac Newton that God must occasionally intervene in the natural course of events to keep the universe running properly. This would suggest, according to Leibniz (who was not a religious skeptic), that an omnipotent and omniscient deity was unable to create a perfect universe on the first try.