His point, made with characteristic eloquence, is that genuine curiosity and honesty have given way to back-slapping or back-knifing sessions, where we laud or condemn according to our prejudices.

McKenzie-Murray is, in some ways, too kind. It is not only the internet, and our politics, that are, as he put it, ''rooted psychologically and enforced by tribal loyalties''. As philosophers and psychologists have argued for centuries, many of our ideas are more habit than reflection. In their very different ways, scholars like Friedrich Nietzsche, Karl Marx and Sigmund Freud make the point clearly: psyche and society alike often rest on irrational or selfish impulses. ''Common sense'' hides partisanships, delusions, and past cruelties polished as present normality. Psychologists have empirically confirmed many of these biases.

On top of this, vice and virtue often grow from the same bulbs: the striving swagger that bolsters the athlete in the pool or ring does not necessarily help with marriage. And good Christian humility can be born of resentment as much as sweetness.

The general point is one familiar to students of the so-called ''hermeneutics of suspicion'': the claims of reason and morality are often overstated. There is much in human nature that is dim, blind and cruel - even when wearing the tweed of reason.

But we cannot overcome prejudices, any more than we can jump over our own shadows. To be human is to be a bundle of dispositions, competing and colluding. Even the self, as Hume noted, is more a tangle of impressions and ideas than anything simple and solid.

However, we can also, as Hume added, have dispositions of analysis, speculation and invention. We can develop, in other words, habits of reason. They cannot take away our irrational urges, but they can make us more mindful of them. We can evaluate our claims, and the anxieties and appetites that give them their psychological vivacity. We can introduce mature plans, checklists, theories, all of which can nudge us to think more patiently and distinctly about ourselves, and the world.

If this smacks of Enlightenment propaganda to you, you are half right: it is an Enlightenment ideal. The finest thinkers of the eighteenth-century, like Voltaire, were certainly committed to reason. But they were not blithe apologists for false rationalism, believing in some utopian world governed purely by reason. They were sceptics, cosmic pessimists, who believed that the world was broken, but could be fixed up, piece by piece. Not because of some inexorable march of logical progress, or because God wanted it thus, but because we are capable of slowly, patiently improving ourselves and the world.

With education, legislation and good communication, we can balance and guide - but never remove - our wild instincts and urges. This is behind Voltaire's famous phrase, from Candide: ''Let us cultivate our garden.'' Despite his rightful scepticism, McKenzie-Murray and other commentators are already committed to this project of social and psychological horticulture. At their best, by participating in the public sphere, they contribute to this gradual enlightenment. If only a few readers make the most of this, this is no fault of authors. Certainly a mood of restless instantaneity does not help. And of course there is rarely any great revelation, in which one's ideological spectacles fall away. But there are moments of consideration and meditation; pauses between reflexes, in which we genuinely consider an idea and its consequences, and try to do it justice.

Yes, reflection depends on mood, education, illness, and a host of other contingencies that colour our consciousness. But reflection is no less possible and valuable for this - being darkly wise is still an achievement.

For the writer, often this is less a task of brimming genius, and more one of rhetorical skill, in Aristotle's sense: knowing how to speak and write intelligently for a particular audience. This has an educational role for the author as well as the audience: being able to craft readable prose means one's ideas can be more easily tested by the public. Instead of enjoying the safety of scholarly solitude, one puts oneself out there.

Despite his pessimism about our brain blinkers, this is exactly what McKenzie-Murray has done, and what he and others are rightly praised for. Not simply for gratifying one's ideological itch, but for putting ideas into the public sphere with charm or punch; for participating in this piecemeal mutual enlightenment. I praise the work, its labours and arts, not always its agreeable bent.

For all the quilts, we are not yet in the sleep of reason.

Dr Damon Young is a philosopher and the author of Distraction: A Philosopher's Guide to Being Free.