Some virtue is painful.
And then we see the equivocation of the inference; for though patience be painful _to learn_, it is not painful _as a virtue_ to the patient man.
The hypothetical, '_If Plato was not mistaken poets are dangerous citizens_,' may be considered as an argument against the laureateship, and may be expanded (informally) thus: 'All Plato's opinions deserve respect; one of them was that poets are bad citizens; therefore it behoves us to be chary of encouraging poetry.' Or take this disjunctive, '_Either Bacon wrote the works ascribed to Shakespeare, or there were two men of the highest genius in the same age and country_.' This means that it is not likely there should be two such men, that we are sure of Bacon, and therefore ought to give him all the glory.

Now, if it is the part of Logic 'to make explicit in language all that is implicit in thought,' or to put arguments into the form in which they can best be examined, such propositions as the above ought to be analysed in the way suggested, and confirmed or refuted according to their real intention.
We may conclude that no single function can be assigned to all hypothetical propositions: each must be treated according to its own meaning in its own context.
Sec.5.As to Modality, propositions are divided into Pure and Modal.

A Modal proposition is one in which the predicate is affirmed or denied, not simply but _cum modo_, with a qualification.

And some Logicians have considered any adverb occurring in the predicate, or any sign of past or future tense, enough to constitute a modal: as 'Petroleum is _dangerously_ inflammable'; 'English _will be_ the universal language.' But far the most important kind of modality, and the only one we need consider, is that which is signified by some qualification of the predicate as to the degree of certainty with which it is affirmed or denied.

Thus, 'The bite of the cobra is _probably_ mortal,' is called a Contingent or Problematic Modal: 'Water is _certainly_ composed of oxygen and hydrogen' is an Assertory or Certain Modal: 'Two straight lines _cannot_ enclose a space' is a Necessary or Apodeictic Modal (the opposite being inconceivable).