Validity as (material!) truth-preservation in virtue of form

According to a standard story, part of what we have in mind when we say that an argument is valid is that it is necessarily truth-preserving: if the premises are true, the conclusion must also be true. But—the story continues—that's not enough, since ‘Roses are red, therefore roses are coloured’, for example, while it may be necessarily truth-preserving, is not so in virtue of form. Thus we arrive at a standard contemporary characterisation of validity: an argument is valid when it is NTP in virtue of form. Here I argue that we can and should drop the N; the resulting account is simpler, less problematic, and performs just as well with examples.