It will at once be obvious, even to those who are least conversant with our theme, that it would be fruitless to attempt the answer to these important questions before we have made a careful survey of the entire history of philosophic thought in Greece. We must have a clear and definite conception of the problems they sought to solve, and we must comprehend their methods of inquiry, before we can hope to appreciate the results they reached, or determine whether they did arrive at any definite and valuable conclusions. It will, therefore, devolve upon us to present a brief and yet comprehensive epitome of the history of Grecian speculative thought. "_Philosophy_," says Cousin, "_is reflection_, and nothing else than reflection, in a vast form"--"Reflection elevated to the rank and authority of a _method_." It is the mind looking back upon its own sensations, perceptions, cognitions, ideas, and from thence to the _causes_ of these sensations, cognitions, and ideas. It is thought passing beyond the simple perceptions of things, beyond the mere spontaneous operations of the mind in the cognition of things to seek the _ground_, and _reason_, and _law_ of things. It is the effort of reason to solve the great problem of "Being and Becoming," of appearance and reality, of the changeful and the permanent. Beneath the endless diversity of the universe, of existence and action, there must be a principle of unity; below all fleeting appearances there must be a permanent substance; beyond this everlasting flow and change, this beginning and ending of finite existence, there must be an _eternal being_, the source and cause of all we see and know, _What is that principle of unity, that permanent substance_, or principle, or being?