“Philosophy is to be studied, not for the sake of any definite answers to its questions, since no definite answers can, as a rule, be known to be true, but rather for the sake of the questions themselves; because these questions enlarge our conception of what is possible, enrich our intellectual imagination and diminish the dogmatic assurance which closes the mind against speculation; but above all because, through the greatness of the universe which philosophy contemplates, the mind is also rendered great, and becomes capable of that union with the universe which constitutes its highest good.”

The History of Freedom in Christianity (1877)

On the question "When and what was responsible for you becoming interested in your academic discipline?" http://www.kcl.ac.uk/aboutkings/governance/equality/meettheprofessors/artshums/mantognazza.aspx, at kcl.ac.uk, 2015.

Source: Tractatus Logico-Philosophicus

The Use of Life (1894), ch. VI: National Education
Source: The Use of Life http://archive.org/details/uselife02lubbgoog/page/n114/mode/2up on Archive.Org, pages 102—103

1940s, Philosophy for Laymen (1946)
Context: There are a number of purely theoretical questions, of perennial and passionate interest, which science is unable to answer, at any rate at present. Do we survive death in any sense, and if so, do we survive for a time or for ever? Can mind dominate matter, or does matter completely dominate mind, or has each, perhaps, a certain limited independence? Has the universe a purpose? Or is it driven by blind necessity? Or is it a mere chaos and jumble, in which the natural laws that we think we find are only a phantasy generated by our own love of order? If there is a cosmic scheme, has life more importance in it than astronomy would lead us to suppose, or is our emphasis upon life mere parochialism and self-importance? I do not know the answer to these questions, and I do not believe that anybody else does, but I think human life would be impoverished if they were forgotten, or if definite answers were accepted without adequate evidence. To keep alive the interest in such questions, and to scrutinize suggested answers, is one of the functions of philosophy.

Source: By Art Koroma, from page 256 of Holy Axiom Truth Exposed... the Bible Is a Myth (2014) note: It appears President Barack Obama started this misattribution. I can find no reference to this quote on the Internet prior to his May 15, 2016 commencement address at Rutgers State University. https://obamawhitehouse.archives.gov/the-press-office/2016/05/15/remarks-president-commencement-address-rutgers-state-university-new

Source: Autobiography (1873), Ch. 2: Moral Influences in Early Youth. My Father's Character and Opinions.