_executory_, when the stipulations remain to be executed, or when one
party agrees to sell and deliver, at a future time, for a stipulated
price, and the other agrees to accept and pay. Contracts are _express_,
when the parties contract in express words, or by writing; _implied_,
when an act has been done which shows that the parties must have
intended to contract; as, when a person employs another to do some
service, it is presumed that the party employing intended to pay for the
labor performed.

Sec.2. Contracts are also distinguished as specialties and simple
contracts. A _specialty_ is a contract under seal; as a deed, or a bond.
But we shall here consider chiefly that common class of contracts called
_simple contracts_, or _contracts by parol_. _Parol_ signifies by word
of mouth. Applied to contracts, however, it not only means verbal
contracts, but includes written contracts not under seal. Both are
simple contracts; the distinction between them is in the mode of proof.
The mutual understanding of the parties to a verbal contract may be
proved by parol evidence. But as the real intention of parties is more
likely to be expressed in a written contract, the rule of law is, that
parol evidence may not be admitted to contradict or vary the terms of a
written instrument. It may however be admitted to explain what is
doubtful, or to supply some deficiency.

Sec.3. To make a valid contract, _the parties must be capable of
contracting_. They must be of sound mind. Hence idiots and lunatics are
generally incompetent to make contracts. Contracts by lunatics and
idiots are not necessarily void, but only _voidable_; the validity or
invalidity depending upon facts to be proved. To avoid a contract on the
ground of mental imbecility, it must be proved that the party
contracting was at the time incompetent. But if a general derangement is
once established or conceded, the person is presumed to be incompetent;
and the party seeking to enforce the contract must prove the other to
have been sane. The general rule in the case of idiots is, that if the
party is incapable of acting in the ordinary affairs of life, or in the
particular contract, his idiocy will annul the contract.

Sec.4. Drunkards also are incompetent to contract while in a state of
intoxication, provided the drunkenness is such as to deprive them of
reason for a time, and create impotence of mind. But for absolute
necessaries, if the drunkard consumes them during