The idea of the Sole Value Assumption is related to anthropocentrism.  The Sole Value Assumption asks if humans are the only species whose interests matter.

Those who agree with the Sole Value Assumption would say yes.  Those who disagree would say that animals, or other parts of nature, matter as well.

If someone accepts the Sole Value Assumption but rejects the Greater Value Assumption, they are a shallow ecologist, according to Richard Sylvan.

Sylvan would call those who reject the Sole Value Assumption, and accept the Greater Value Assumption, Intermediates.

However, if a person rejects both theories, they are called a deep ecologist.  The distinction between deep and shallow ecologists was also made by Arne Naess.

The principal reason for opposing the Sole Value Assumption is that animals are capable of suffering.  A person might then think that value exists in preventing that suffering, implying that the interests of animals are important as well.