Both empirical data and theoretical approaches suggest that argumentation is an important component of development of reasoning skills. We argue that if argumentation does have a primary role, then children should be able to distinguish more from less logical justifications even when they are incapable of determining the correct conclusion by themselves. We asked 8- and 11-year-old children to choose one of two conclusions for abstract reasoning problems, based on justifications from authority (friends and teacher) or logical ones (probability and counterexamples). Although there was a clear age-related increase, even the younger children considered logical justifications to be better than authority, irrespective of the specific conclusion endorsed. Thus, children can distinguish logical and non-logical justifications even when they cannot easily arrive at the correct conclusion by themselves.