Chimpanzees can master rudimentary sign language. Dolphins have an intricate communication system that resembles a fully fledged, if simple, language. Even some birds - which we often misinterpret as dumb (think insulting terms such as 'bird brain') - can learn up to dozens of words. Animals' intelligence and cognitive ability have raised questions about whether they deserve to have some rights formally recognised in law. The famous Princeton philosopher Peter Singer is a prominent advocate of animal rights. As he argued in an opinion column in the Post yesterday, at the very least our closest cousin, the chimpanzee, deserves recognition of the rights to life, liberty and protection from torture because they are self-aware and have emotional lives. But it may be argued that Singer does not go far enough because of the contemporary emphasis on rights as entitlements. This is often contrasted with the alleged Chinese or oriental understanding of rights as obligations. Both ways of understanding rights are limited and one-sided. Think of rights as a kind of investment, which always requires a counterparty to absorb a loss. A citizen's entitlement (a right) requires a guarantee by a credible counterparty, usually the state. On the other hand, his obligation (say, military draft) is also usually imposed by the state (which enjoys the right to do it). Apply this moral scenario to animals or our stewardship of the earth itself. This does not require animals to be smart or self-aware. All that it needs is that humans recognise their counterparty obligation to the well-being of animals - and of the earth itself. We know what we have done to Mother Nature - and ourselves - by our refusal to honour our privilege and obligation as the alpha species.