If I’d researched this more carefully, I would never have bought this book. It was a good title, it’s a shame it’s all centred on Kantian ethics. The writer’s dismissal of Hume didn’t seem to appreciate the depth of Hume’s criticism, missing the quote “Tis not contrary to reason to prefer the destruction of the whole world to the scratching of my finger. Reason's only purpose is to help us to satisfy our desires. Reason is, and ought only to be, the slave of the passions.” This whole statement has been validated as a psychological fact, one need only read “The Righteous Mind” by Jonathan Haidt, “Descartes’ Error” by Antonio Damasio and “Thinking, Fast and Slow” by Daniel Kahnemann to see that architecture of human minds requires emotional responses to function, that without emotions we cannot care enough to make moral decisions and that human rationality is subject to systematic biases that make Kant’s call to reason a quaint antiquated relic of a utopian vision. I confess, I never managed to make it to the point where maturity was assessed in these terms, aborting my effort halfway through, but then again, with such systemic issues in the basis for assessment, why would I give any credence to the conclusion.