If you want to become a better person, you ought to study the philosophy of Baruch Spinoza. That at least is the message of Steven Nadler’s delightful new book, and it may seem rather surprising. Spinoza’s bottom line was that mind and body are inseparable, that the entire world is a single unitary substance and that everything in it, from the stars and planets to our bodies, brains, thoughts and actions, is governed by inexorable fate. We may lose a night’s sleep trying to work out where our moral duty lies, but in reality our deliberations and decisions have been pre-programmed since the beginning of time, and nothing could have fallen out differently. ‘We are pushed hither and thither by external causes,’ as Spinoza put it, ‘tossed about like waves on the sea, and driven by contrary winds, and we never know where we are going.’ It follows that the idea of free will is nonsensical. You might well conclude that the whole business of moral self-improvement is a sham.

That, however, would be a mistake. The freedom that matters in morality, Spinoza says, is not freedom of will but freedom of intellect. And intellectual freedom rests not on arbitrary choices but on what he called ‘fortitude’, meaning mental resilience