Every aspect of experience that can be reified. that is, regarded as thing-like, insofar as being consituted of 'qualia', and that is unchanged by being so regarded, can be equated with representation, or seen as essentially mental. Not everything need be like that, however. The consistent causal structure of the world is enactive and loses its effectiveness when viewed at one remove, in a 'dissociated' manner. Since this is often a matter of life and death, in as banal case as crossing a bust street, idealism is seen as a luxury for enjoyment only at leisure. In addition, many of the best arguments for idealism rely on a tautologous understanding of the borderlessness of consciousness. If you take away everything that can be known or experienced about things you are left with a complete void of any relevance, and therefore there can be nothing more to reality than what can be known and experienced. This denies one of the most common facts which is that consciousness is entirely filled up with things of which it has absolutely no notion how they got there.