I read this book years ago when it first came out and it changed my life. Bartley extends Popper's critical rationalism to what he calls 'Pancritical Rationalism'. Justficationists, as opposed to falsificationists, ultimately hold to some kind of presuppositionalism. However, the presuppositions are held for non-rational reasons. They justify this by claiming that everyone supposedly has to do this -- their defense is 'to quoque...you too'. Bartley claims a way out is to hold these presuppositons heuristically and non-dogmatically. If they are open to revision and lead to interesting claims that can be disconfirmed by experience ( modus tollens ) then you can claim to be rational. If your persuppositions can never be revised and you will go to your grave defending them, then you are not a rational person.
Bartley uses the history of Protestant Christianity ( Catholicism has never claimed to be rational ) as an example of a rational scientific world-view that turned itself into an irrational ideology in order to defend( save ) itself against modern science. This is the section that had the greatest impact on my life ( for the best ). I realized in order to be rational I had to give up my faith based ideas or forever resort to irrationally ( and dogmatically) held first principles to to defend my position.
No longer can religionists retreat back to 'faith' as a defense of their position. Notable examples of presuppositionalists who still ignore this critique are Alvin Platinga, Karl Barth ( any of the neo-orthodox really ) and the Reformed theologians following in the footsteps of Cornelius Van Til. Pannenberg and some others claim to take this critique seriously, but when you read them, they provide no strong evidence but instead, resort back to faith in the end. ( )

WW Bartley, III, was one of my three (3) Faculty advisors in college. In marquis's Who's Who, Dr. William Warren Bartley, III, pioneered CCR - comprehensively critical rationalism. ( )