The sense of national honour; the pride of blood, the tenacious spirit of self-defence, the sympathies of kindred communities, the instincts of a dominant race, the vague but generous desire to spread our civilisation and our religion over the world; these are impulses which the student in his closet may disregard, but the statesman dares not....'[36] [36] Herman Merivale, _Colonisation_, 1861, 2nd edition.

The book is a re-issue, largely re-written, of lectures given at Oxford in 1837.

The passage quoted forms part of the 1861 additions, p.

675.
What does 'abstract political philosophy' here mean?
No medical writer would speak of an 'abstract' anatomical science in which men have no livers, nor would he add that though the student in his closet may disregard the existence of the liver the working physician dares not.
Apparently Merivale means the same thing by 'abstract' political philosophy that Mr.Bryce means by 'ideal' democracy.

Both refer to a conception of human nature constructed in all good faith by certain eighteenth-century philosophers, which is now no longer exactly believed in, but which, because nothing else has taken its place, still exercises a kind of shadowy authority in a hypothetical universe.
The fact that this or that writer speaks of a conception of human nature in which he is ceasing to believe as 'abstract' or 'ideal' may seem to be of merely academic interest.