In Brief

Sir: Alasdair Mitchell (letter, 28 July) claims to have uncovered "the great flaw in the doctrine of innate animal rights" - the difficulty in determining which creatures are capable of suffering. The capacity of non-human vertebrates to experience pain is beyond reasonable doubt. It's also probable that higher invertebrates - such as crustacea - can suffer; and it's possible that lower invertebrates possess some level of sentience. Such marginal cases do not, however, justify the exploitation of those creatures - primarily vertebrates - whose capacity for suffering is not in dispute.

PAUL REES

Whitstable, Kent