In logic, Antisthenes was troubled by the problem of the One and the Many. As a proper nominalist, he held that definition and predication are either false or tautological, since we can only say that every individual is what it is, and can give no more than a description of its qualities, e. g. that silver is like tin in colour. Thus he disbelieved the Platonic system of Ideas which do not exist save for the consciousness which thinks them. ""A horse"", said Antisthenes, ""I can see, but horsehood I cannot see."" Definition is merely a circuitous method of stating an identity: ""a tree is a vegetable growth"" is logically no more than ""a tree is a tree.