It is known that content has an effect on reasoning. In this paper the influence of the content on the structure of reasoning, the access to it, and the ability to handle uncertainty was studied. The participants were presented with reasoning tasks about the weather and about the oscilloscope in which uncertain premises were introduced. Correct reasoning procedures were identified including correct reasoning with wrong answers. In correct reasoning procedures about the weather, three different structures of reasoning were identified. The participants were mostly able to reason with uncertain components. In reasoning about the oscilloscope, less correct reasoning procedures were found. No empirical and theoretical structures were used. The hidden structure differed here from the one in the weather case because the participants were not able to handle all uncertain components in otherwise correct reasoning. The implications of this unique finding for the acquisition of reasoning skills are discusse
