'mature thought' is correct and usable in written English.
You can use it when you want to express the idea of an opinion that has been formed due to experience and reflection. For example: "Through much reflection and experience, he had formed a mature thought on the subject."
Most of the themes of Calvin's mature thought were contained in the first edition.
The cultural conflict between East and West that had its vortex in Vienna's cosmopolitan intellectual life and the sense that liberal culture was on the verge of being undermined, were reflected throughout Freud's mature thought.
Originally delivered as the Cambridge Conferences Lectures of 1898, Reasoning and the Logic of Things is the most accessible and thorough introduction to Peirce's mature thought to be found within the compass of a single book.
It was in Prague that his mature thought developed.
This has also been claimed for the Elements of Theology, which, however, shows all the sophistication of Proclus's mature thought.
In understanding the extent to which recognition of evil pervades Marx's mature thought, the centrality to his analysis of the notion of "exploitation" deserves emphasis.
Some of Ives's mature thoughts about music owe a lot to Phelps's example.
McCalman notes significant observations that prefigured each man's mature evolutionary thought.
The smaller the tomato the quicker it will mature, a thought to keep in mind if you live in a cool part of the country.
With its theme of former gang members coming to terms with the ramifications of their decisions as teenagers, this is the most mature and thought-provoking of Noel Clarke's urban drama series.
Augustine's magnum opus, "The City of God," is a product of this mature period of thought.
