 The contradiction might also vanish if propositions in scientific theory have unusual meanings.  One option is that universal affirmatives are understood in scientific theory as universalized conditionals, as they are understood today.  This would not interfere with the fact that they are not conditionals in uses outside of scientific theory.  Although De Rijk (1973, 52) states that Ockham holds such a view, he seems to explicitly reject it, stating that ‘A human is a rational animal’ is not equivalent to ‘If a human is then a human is a rational animal “because this is a conditional and not a categorical”. [Ockham SL II.11]