What would happen if the great Scots philosophers David Hume and Adam Smith were, upon their deaths, propelled from the late 18th century to the early 21st?

This is the tantalising question proposed by Jo Clifford's new play The Tree Of Knowledge.

The answer, predictably enough, is that they would be profoundly disappointed that the promise of Smith's morally enlightened capitalism had been so utterly subverted and that Hume's dream of emancipation through knowledge and liberty had not been realised. Ironically, Clifford has manifested one of the greatest dangers inherent in the Enlightenment; namely that it would lead to a drama in which moral indignation and instruction masqueraded as art.

In fairness, her piece begins auspiciously enough. The opening 10 minutes – in which Hume (played by a hilariously disbelieving Gerry Mulgrew) is confronted with the likelihood that his flesh-and-blood arrival in the 21st century has disproved his assertion that there is no life after death – are very funny indeed.

But the jokes soon wear themselves out and the addition of Eve (a supposed modern "Everywoman", played by the fine actress Joanna Tope) is especially misjudged. Despite surviving violent abuse by her father and husband, she is the most insipid of characters. Her increasingly cloying speeches point, with depressing inexorability, towards a polemically liberal conclusion in which she invokes Einstein and Buddha.

Ultimately, this drearily static play has only one real protagonist (the hyperactive Smith), where three are presumably intended. Ali Maclaurin's horrible set (a 1970s vision of concrete futurism) offers an appropriate visualisation of a theatrical shambles.

The Tree Of Knowledge

Traverse, Edinburgh, until December 24

Reviewed by Mark Brown