Petrarch was not able to read Plato directly, but he greatly admired him. Petrarch was also a great admirer of Roman poets such as Virgil and Horace and of Cicero for Latin prose writing. Not all Renaissance humanists followed his example in all things, but Petrarch contributed to a broadening of his time's 'canon' (pagan poetry had previously been considered frivolous and dangerous), something that happened in philosophy as well. In the sixteenth century anyone who considered himself 'au fait' read Plato as well as Aristotle, trying as much as possible (and not always very successfully) to reconcile the two with each other and with Christianity. This is probably the main reason why Donato Acciaiuoli's commentary on Aristotle's "Ethics" (first published in 1478) was so successful: it blended the three traditions beautifully.