into two groups: propositions of policy, and propositions of fact. The
first class consists of those propositions that aim to prove the truth
of a theory, that indicate a preference for a certain policy, for a
certain method of action. The second class comprises those
propositions that affirm or deny the occurrence of an event, or the
existence of a fact. Propositions of policy usually, though not
always, contain the word _should_ or _ought_; propositions
of fact usually contain some form of the word _to be_. The
following illustrations will make the distinction plainer:--


PROPOSITIONS OF POLICY.

The United States should adopt a system of bounties and subsidies for
the protection of the American merchant marine.

State laws prohibiting secular employment on Sunday should be
repealed.

A city furnishes a more desirable location for a college than the
country.

The aggressions of England in Africa are justifiable.


PROPOSITIONS OF FACT.

Homer wrote the Iliad.

Nero was guilty of burning Rome.