After what I said about Aquinas and Clarke in my previous post, you might be thinking something like this about them, “While their arguments aren’t very convincing to us today, they were at least good arguments in the context they were given, at a time when more people shared the assumptions behind the arguments.”
But I’m not sure that’s right. As far as I can tell, the assumptions behind Aquinas’ and Clarke’s arguments really were more popular in their day than in ours, but I’m not sure the fact that we’ve gotten rid of those assumptions is the main reason arguments in the style of Aquinas and Clarke are no longer as popular as they once were. There’s another big change that’s happened since their day: it’s become safe to doubt the existence of God.
Aquinas himself advocated executing heretics, and the church of his day condemned many of Aristotle’s views as heresy. In the Summa Theologiae, Aquinas himself often notes ways in which Aristotle’s views seem to conflict with Christianity, but his response is always, roughly, “Aristotle didn’t really mean that, he really meant something else.” What would the history of philosophy be like, if it had been safe for more heretical medieval Aristotelians to defend their views at length, the way Aquinas did?
In the 17th and 18th centuries, European society became more liberal, but only gradually. The philosopher Thomas Hobbes (1588-1679) was nearly executed for blasphemy because his political treatise Leviathan said some seemingly unorthodox things about religion (Hobbes said we can know by reason that God exists, but we can’t know much about him).
The last execution for blasphemy in Britain was in 1697, but even after that it could be risky to cast even a little bit of doubt on the claims of religion. David Hume appears to have lost out on a job as a professor at the University of Edinburgh because his ideas were perceived as undermining traditional arguments for the existence of God. Hume hadn’t publicly denied God’s existence, or even publicly criticized the arguments for the existence of God. The fact that his philosophical ideas could undermine them was enough.
Hume later wrote the Dialogues Concerning Natural Religion, which is generally seen as being meant to criticize arguments for the existence of God. Hume tried to hide his own ideas behind a set of fictional characters, but in spite of this, Hume’s friends thought the book was too dangerous to publish, and talked him out of publishing int during his lifetime.
So it’s not surprising that in the 17th and 18th centuries, all the most influential philosophers until Hume agreed that the existence of God could be proved through reason. This includes Descartes (1596-1650), Spinoza (1632-1677), Locke (1632-1704), Leibniz (1646-1716), and Berkeley (1685-1753).
A few people did publicly question the arguments for the existence of God, but they risked being accused of atheism. That’s the problem with outlawing doubt: you then have to be suspicious even of people who claimed to be believers. Pierre Bayle (1674-1706), for example, defended religious freedom, praised the moral character of Spinoza, and had a lot to say on the problem of evil, but claimed to accept Christianity on faith. To this day, historians aren’t sure what he really believed.
Towards the end of the 18th century, Kant rejected all the traditional proofs of the existence of God in his Critique of Pure Reason, but said we should believe in God as a “postulate of practical reason.” And then, when you look at the history of philosophy after Kant, it becomes much harder to find important philosophers who accepted any argument for the existence of God. You even start to see openly atheistic philosophers like Schopenhauer (1788-1860).
So in short, back when it wasn’t safe to cast doubt on religion, philosophers generally agreed that the existence of God could be proven. But once doubt became safe, the arguments became much less popular. That’s worth remembering when we look at the history of philosophy.
When we find a “great” thinker like Aquinas advocating violence to silence those who disagreed with him (it’s almost always a him), we should be suspicious. We should wonder: did he really make it into the history books because his ideas were so good? Or was it simply the fact that it was his team that successfully used threats of violence to make the other side shut up, rather than the other way around?