But his studies, since his return from Germany, had been directed to metaphysics, and especially to the philosophical bases of poetry and theology; and the last twenty years of his life, at least, were occupied with plans for a great philosophical work covering these two fields of thought.

One of the fragments of the great work that actually came to light, the _Biographia Literaria_, seems to have been sent to the printers in 1815.

A collected edition of his poetry was also begun while he was under the Morgans' care.
From 1816 till his death in 1834 he lived in comparative peace, if not in happiness, with a Mr.Gilman of Highgate near London, an apothecary.
Gilman and his wife were able so far to wean him from the drug, or to regulate his use of it, that he brought to the birth something of his vast plans in criticism and philosophy, notably the _Biographia Literaria_ (1817) and the "Aids to Reflection" (1825).

The beginning of his stay with Gilman was also marked by the publication of "Christabel" and "Kubla Khan" (1816), and of a collected edition of his other poems (including "The Ancient Mariner," considerably revised) under the title "Sibylline Leaves" (1817).

But the poems that were not finished in the first great period at Stowey remained unfinished.