"After experience had taught me that all the usual surroundings of social life are vain and futile; seeing that none of the objects of my fears contained in themselves anything either good or bad, except in so far as the mind is affected by them, I finally resolved to inquire whether there might be some real good having power to communicate itself, which would affect the mind singly, to the exclusion of all else: whether, in fact, there might be anything of which the discovery and attainment would enable me to enjoy continuous, supreme, and unending happiness."[153:5] In pursuance of this aim, though he deals with the problem of being in the rigorous logical fashion of his day, the final words of his great work are, "Of Human Freedom": "Whereas the wise man, in so far as he is regarded as such, is scarcely at all disturbed in spirit, but, being conscious of himself, and of God, and of things, by a certain eternal necessity, never ceases to be, but always possesses true acquiescence of his spirit. If the way which I have pointed out as leading to this result seems exceedingly hard, it may nevertheless be discovered. Needs must it be hard, since it is so seldom found. How would it be possible if salvation were ready to our hand, and could without great labor be found, that it should be by almost all men neglected? But all things excellent are as difficult as they are rare."[154:6] [Sidenote: Philosophy as the Extension of Science.] § 58. On the other hand, one who looks to philosophy for the extension and correction of scientific knowledge will be primarily interested in the philosophical definition of ultimate conceptions, and in the method wherewith such a definition is obtained. Thus the philosophy of the scientist will tend to be logical and metaphysical. Such is the case with Descartes and Leibniz, who are nevertheless intimately related to Spinoza in the historical development of philosophy. "Several years have now elapsed," says the former, "since I first became aware that I had accepted, even from my youth, many false opinions for true, and that consequently what I afterward based on such principles was highly doubtful; and from that time I was convinced of the necessity of undertaking once in my life to rid myself of all the opinions I had adopted, and of commencing anew the work of building from the foundation, if I desired to establish a firm and abiding superstructure in the sciences."[155:7] Leibniz's mind was more predominantly logical even than Descartes's. He sought in philosophy a supreme intellectual synthesis, a science of the universe.