The phrase "rational justification" means providing logical reasoning or evidence to support a belief, decision, or action. It involves using logical thinking and sound arguments to explain why something is reasonable or justified. Full definition
Stop passing laws based entirely on your fairy tales without rational justification and we can get along. (religion.blogs.cnn.com)
It was from Collingwood, as he indicates in the prologue to the third edition of After Virtue, that he came to recognize that «what historical enquiry discloses is the situatedness of all enquiry, the extent to which what are taken to be the standards of truth and of rational justification in the contexts of practice vary from one time to another.» (firstthings.com)
They think his view that standards of truth and of rational justification in the contexts of diverse practices and inquiries means he has little defense against relativism. (firstthings.com)