In 1794 Cowper was again insane and his lifework was over.
If Elijah is the prophet of the fall of Omri's dynasty, Elisha is no less the prophet of Jehu and his successors; and it is extremely probable that his lifework was confined to the dynasty which he inaugurated.'
It was not till 1788 that he made the acquaintance of the Kantian philosophy, which was to form the basis of his lifework, and as early as 1790 he published the Versuch fiber die Transcendentalphilosophie, in which he formulates his objections to the system.