Darwinism and its Discontents, by Michael Ruse (CAMBRIDGE UNIVERSITY PRESS £19.99 (328pp) £17.99 (free p&p) from 0870 079 8897) Darwin Loves You, by George Levine (PRINCETON UP £18.95 (336pp) £16.95 (free p&p) from 0870 079 8897)

As Charles Darwin grew old, he lamented his estrangement from poetry. As a young man he had loved his Milton, Coleridge and Shelley; he had taken "intense delight" in Shakespeare. "But now for many years I cannot endure to read a line of poetry: I have tried lately to read Shakespeare, and found it so intolerably dull that it nauseated me." His loss of aesthetic feeling progressed as his scientific publications accumulated; and so did his distance from religious belief. Did his science induce anaesthesia and atheism? In a post-Darwinian landscape, must we see only algorithms and machines?

An answer can be found in the phrase coined by the neurophysiologist Charles Sherrington in the 1930s, when he imagined the brain as an "enchanted loom". Although looms are often props in folktales, they are prosaic and mechanical; yet there is nothing incongruous in the idea that one might be enchanted. If that is true for a clattering repetitive mechanism, it should remain immeasurably truer for the replicating, evolving systems that we know as life.

It is salutary and character-building to read those caustic mechanicals Daniel Dennett and Richard Dawkins; but it is also important to appreciate that their algorithms and machines are not all there is to see in the Darwinist landscape.

That is where these two books come in. They differ in their strategies: Darwin Loves You, written by a professor of English, explores Darwinism within Darwin's person and writings, while Darwinism and its Discontents, by a historian and philosopher of science, is a concise course in the history of evolutionary thought and its implications.

In Darwin Loves You, subtitled "Natural Selection and the Re-Enchantment of the World", George Levine frets over whether he is working from the texts or speaking from his own sentiments. Like Darwin himself, he is immersed in his details and chronically uneasy about his relationship with them. This is a predicament familiar to many writers, and perhaps a reason why literary critics are so drawn to Darwin.

Michael Ruse, by contrast, is a lecturer rather than an essayist. He bases his confidence not on the figure of Darwin but on the body of knowledge constructed on Darwin's foundations. In each chapter he recounts tests to which that body has been subjected, and each time reports that it has passed.

Levine likewise conveys a profound sense of the truth of orthodox Darwinism. Both books affirm the science while demonstrating that it is also a social construct. Perhaps it's not too much to hope that one day such a position will no longer be so unusual that it needs to be remarked upon.

Ruse draws heavily on the textbooks for his examples: it is in its range, from palaeontology to philosophy, that his book distinguishes itself. Although his conclusions are convincing, his discussions do not venture very far into dangerous territory, such as sex or race, and are sometimes not as clear as his direct prose makes them appear.

Readers may get the false impression that researchers who have found stepchildren to be at far higher risk than others of domestic violence have argued that this results from an evolved tendency to harm non-kin. They actually see it as a malignant absence of parental feeling.

And ending a chapter on literary responses to Darwinism with Ian McEwan would have been more pertinent if it had mentioned Saturday after dwelling on Enduring Love. In the earlier novel, Ruse argues, McEwan suggests that Darwinism implies biological determinism, but also that humans can rise above their biological selfishness. In the more recent novel, McEwan's bourgeois paragons seem to imply that the ability to behave as a good person depends on having good genes.

What would Darwin say? He would widely be assumed to have spoken in the callous tones of what came to be known as Social Darwinism, a view of life that had relatively little to do with him. Levine seeks to reveal a "kinder, gentler Darwin": not just the loving father and basically nice guy that emerge from his personal chronicles, but also somebody whose love for the world remained constant even as he came to understand its harshness and indifference.

Darwin's relationship with nature belonged to the Romantic tradition of ardent wonder, even as he transcended the mists of Romantic illusion to produce a materialist account of the living world. As 1066 and All That might have put it, Darwin was both Romantic and Right.

Dawkins might respond that this secular sense of wonder is precisely what he has been on about for years. But it depends how that sense is expressed. Levine - for whom secularity has been "the condition of a liveable nation" - attends to the affect of what he reads. An immensely sympathetic reader, he finds in Darwin depths of sympathy that may elicit responses rather than reactions from people who share a deep concern about the resurgence of religiosity around the world.

Darwin Loves You combines passion, subtlety, critical scrutiny and moral purpose. Levine suggests that Darwin was alienated from poetry because it was excessively human, failing to acknowledge nature's indifference.

Maybe; or maybe it was a Darwinian effect, an ageing nervous system drained of the intensity needed to fuel a young man's ardour. Or perhaps, as it seemed to Darwin, his mind had "become a kind of machine for grinding general laws out of large collections of facts".

Darwinian thinking can seem to take the life out of the imagination - as Levine inadvertently suggests by rendering Darwin's famous line "There is grandeur in this view of life" as "this view of things". But even if poetry eventually seemed to him too full of conceits, Darwin surely remained an enchanted Romantic to the end of his days; and Levine is surely right to see hope for our own times in an avowedly Romantic Darwinism.

Marek Kohn's 'A Reason for Everything: Natural selction and the English imagination' is published by Faber & Faber