 The elimination of matter as a good candidate for being substance, leaves either form alone or the composite of form and matter. The composite seems more consonant with the doctrine of Categories, for the composite is the individual. Aristotle, however, chooses the form as more paradigmatically substance. This has puzzled some commentators. Wiggins (1998: 232ff), for example, thinks that the change in doctrine between Categories and Metaphysics is wholly unhelpful. The choice of form as substance causes perplexity because the form seems to be a universal and equivalent to the secondary substance, and so not the most fundamental case of substance. But whether substantial forms are universals in Aristotle is a controversial matter. Interpreters disagree about whether the doghood that is in Fido is best regarded as the universal, or as the particular instance of the universal doghood, other dogs exemplifying numerically different instances of the same universal (for example, Lloyd 1981, Irwin 1988, Woods 1991, and Bostock’s commentary to Aristotle 1994). On this view, the most perspicuous way of regarding the individual substance is not as the composite of form and matter (though this is not wrong) but as the form individualised in the matter. The matter is still an essential component in the substance, but not, so to speak, as an equal partner with the form, but as the catalyst by means of which the form becomes an individual substance. It is clear, however, that if one holds that Aristotle thinks that forms are universals, then forms are not substance, for, in his attacks on Plato, Aristotle makes it plain that universals are not substance. Substances for Aristotle are individuals, but it is much debated whether they are individualised forms or composites of form and matter.