I regard philosophy as a search for coherence, or some closely related term, though certainly not "truth" in the sense of exclusive correct answers to philosophical problems. The kind of coherence we look for may be primarily rational-cognitive-scientific in some instances, and aesthetic-evaluative-creative in others (and also practical-moral - I think that covers the three Critiques!) But really I don't think there is much of a dichotomy in practice. Scientific reasoning involves both; any physicist worth his weight in Higgs bosons knows that. So does philosophical argument.

So, fine, you can have "coherence" as a criterion of evaluation if it is understood properly. But it is not, usually. I had one quite well-known professor who insisted that every line of argument in every paper you write must be readily reducible to a piece of formal logic. The same professor insisted that counterexamples are the heart of philosophical argument. I disagree with him on both points. These views overemphasize one particular kind of coherence that has become an academic shibboleth. This is precisely what I mean by scholasticism. It is rare to have it articulated quite so explicitly, but it is out there in force nonetheless.

I highly recommend another reading of On Certainty if it is more than 5 years since you last visited it. :-)