Hm, more Chesterton. Insty linked to this search for a famous not-quotation; an actual attributed one is this:
A man who refuses to have his own philosophy will only have the used-up scraps of somebody else’s philosophy. [“The Revival of Philosophy,” The Common Man (1930)]
Ayup. Lots of people out there who have no philosophy, just pre-digested Positions that they hold dear for reasons they are unable to explain. Lacking a philosophical basis for their positions, they are reduced to shouting.
Or, as Kipling wrote:
We have threshed a stook of print and book, and winnowed a chattering wind
And many a soul wherefrom he stole, but his we cannot find:
We have handled him, we have dandled him, we have seared him to the bone,
And sure if tooth and nail show truth he has no soul of his own.