 Following Boethius, many authors referred to a modal distinction based on a triple matter of assertoric sentences, namely natural, contingent, or remote. In a sentence of natural matter, the predicate belongs essentially to the subject or is its proprium, in contingent matter, the predicate may belong or not belong to the subject, and in remote matter, the predicate cannot belong to the subject. See, for example, Peter of Spain, Tractatus, p. 7; Dialectica Monacensis 472.9–473.22. According to Garland the Computist (11th century), the opposite universal sentences of contingent matter are both false and the opposite particular sentences are both true (Dialectica, 54.21–30; 82.25–30). The same division of the sentences of contingent matter based on the frequency interpretation of contingency is found in Aquinas (In Periherm. I.13, 168). See also Boethius, In Periherm. II, 177.18–178.8; 303.15–306.13; 325.8–15. Another often discussed theme was the distinction between modalities per se and per accidens, which was based on the idea that the modal status of a temporally indefinite sentence may be changeable or not; for example, ‘You have not been in Paris’ may begin to be impossible, whereas ‘You either have or have not been in Paris’ may not. (See, for example, William of Sherwood, Introduction to Logic, 41). Another distinction between sentences necessary per se and per accidens was based on Aristotle’s theory of per se predication in Posterior Analytics I.4. A sentence was said to be accidentally necessary when it was unchangeably true but, as distinct from per se predications, there was no necessary conceptual connection between subject and predicate. This became an important part of thirteenth-century interpretations of Aristotle’s modal syllogistics. (See, for example, Robert Kilwardby’s Notule libri Priorum 8.133–142; 40.162–174.)