J.S. Mill on poetry... note the date!

It has often been asked, What is Poetry? And many and various are the answers which have been returned. The vulgarest one of all — one with which no person possessed of the faculties to which poetry addresses itself can ever have been satisfied — is that which confounds poetry with metrical composition; yet to this wretched mockery of a definition many have been led back by the failure of all their attempts to find any other...

the word ‘poetry’ imports something quite peculiar in its nature; something which may exist in what is called prose as well as in verse; something which does not even require the instrument of words, but can speak through the other audible symbols called musical sounds, and even through the visible ones which are the language of sculpture, painting, and architecture

John Stuart Mill, "Thoughts on Poetry and its Varieties", 1833