In the tug of war between personal and sub-personal accounts of man, Scruton pulls, with body and soul, for Team Personal. As the title of Daniel C. Dennett’s new book, From Bacteria to Bach and Back: The Evolution of Minds (Allen Lane, £25), suggests, he, in contrast, sees his fundamental philosophical task as understanding how our sub-personal parts add up to the personal whole. He would probably view Scruton’s poetic account of our nature as grist to his mill: it’s interesting, if a little strange, the way things seem to Roger — let’s see if we can work out how they can possibly have ended up seeming like that! Scruton is distrustful of “genealogical” theories of man: for Dennett they are crucial.

This large, engaging, digressive book is a grand reprise of Dennett’s output, though he does not rest on his laurels: they still put out plenty of buds. If you have not encountered his work, you surely should: like him or loathe him, very few contemporary thinkers have supplied us with so many “thinking tools”. He sets himself three main challenges here: to make sense of the idea of Design without a Designer that is so central to understanding evolution; to flesh out the concept of competence without comprehension, the key to much animal — and indeed human — thought and behaviour; to understand human consciousness as a natural, unmysterious, outcome of i) evolutionary design, ii) uncomprehending competence and, iii) a little something extra, shortly to be revealed. The overarching task is to enable us to understand ourselves, the intellectuals of creation, as the products of gradual, natural, processes, issuing out of dust yet eschewing the hand of God.

One of Darwin’s 19th-century critics, Robert MacKenzie Beverley, nicely captured the first of Dennett’s ideas, though with the intention of deriding it, writing sarcastically: “in order to make a perfect and beautiful machine, it is not requisite to know how to make it”. Beverley was indignant at this “strange inversion of reasoning”, which assumed “Absolute Ignorance fully qualified to take the place of Absolute Wisdom in all the achievements of creative skill”. But Darwin’s theory, envisaging a process by which natural selection from a pool of possibilities, themselves created by random mutations, gives rise over time to adaptation in organisms and the appearance of design, explained precisely how this strange inversion of reasoning could be justified. As a result of natural selection, the biosphere came, in Dennett’s words, to be “utterly saturated with design, with purpose, with reasons” long before there were minds to entertain any of these: indeed, the effect of Dennett’s broad line of explanation for the way things are is to replace an ancient “mind-first” with a modern “mind-last” vision of creation.

But once there was life, and especially living things that moved, nervous systems, and with them minds, became useful, to enable “swift control”. One of Dennett’s most appealing sets of thinking tools is his series of distinctions between different “kinds of mind”. Darwinian creatures rely on instinct: the bee conveying information about the distance, direction and quality of a food source to its companions by way of its waggle dance is in this category of animals born “gifted but not learners”, a prime example of “competence without comprehension”. Skinnerian creatures, named after the behaviourist psychologist B.F. Skinner who studied learning in rats, are designed to try things out: without much premeditation they produce a variety of behaviours, some of which life rewards while others it punishes — they learn accordingly. Popperian creatures, honouring Karl Popper, the philosopher of science, let “their hypotheses die in their stead”: they model the world in their heads and can test out possible solutions ahead of time. But only we are Gregorian creatures, named after the psychologist of vision, Richard Gregory, users of “thinking tools” from the humble, old-fashioned word to the ubiquitous iPhone.