The Incoherence of Believing in Something (but you aren't quite sure what).

Richard G Swinburne

In the opening lines of Swinburne's introduction to his book "The Coherence of Theism" he states that by a theist he understands a man who believes there "is something like a person without a body (i.e. a spirit) who is eternal, free, able to do anything, is perfectly good, is the proper object of human worship and obedience, the creator and sustainer of the universe."

This immediately begs the question of what, if anything, is "like a person without a body". This question-begging is only compounded by the additional qualifications that follow in the statement. 

A few lines down Swinburne also reveals his conclusion that "the question of coherence of belief that there is a god cannot be separated from the question of its truth".

So the void Swinburne opens up at the beginning of the introduction is later revealed to be bottomless at its end.

His book is 324 pages long. That's "Philosophy of Religion" for you.