Original impossibility may be either subjective or objective; may be temporary or permanent: may be partial or absolute, sec 296.

Subsequent impossibility may be either culpable or non-culpable; temporary or permanent; partial or absolute, sec 297.

Non-existence of thing at the time a defence, sec 298.

And so of non-alienability of thing disposed of, sec 299.

When essential quality of thing promised is destroyed, contract is void, sec 300.

When both parties know of impossibility, this avoids, sec 301.

If promisor knows or ought to know of impossibility, this is no defence, sec 302.

Otherwise, when promisee knows or ought to know of impossibility, sec 303.

Mere improbability does not vacate, sec 304.

Subsequently occurring legal prohibition a defence, sec 305.

Otherwise as to foreign prohibition, sec 306.

Legal impossibility induced by promisor's negligence no defence, sec 307.

Casus is a disaster which due diligence could not avert, sec 308.

No defence when negligently encountered, sec 309.

But perfect caution not required, sec 310.

Casus not a defence when the risk is one promisor took, sec 311.

Party making performance of a contract impossible cannot complain, sec 312.

Casual impossibility must be permanent and absolute, sec 313.

Impossibility of delivery a defence, sec 314.

But not of fungible things, sec 315.

Subsequent non-producibility of goods a defence, sec 316.

After completion of sale loss falls on purchaser, sec 317.

Covenant of tenant not defeated by casus, sec 318.

Exception in case of public war, sec 319.

Casus a defence to suit against bailee, sec 320.

Bail bonds and other guarantees relieved by casus or necessity, sec 321.

Subsequent impossibility a defence to a suit on contract for work, sec 322.

Subjective incapacity no defence to duty not exclusively personal, sec 323.

Incapacity for marriage a defence to an engagement to marry, sec 324.

Incapacity self-inflicted no defence, sec 325.

Work to be paid for though thing is subsequently destroyed, sec 326.

Common carrier may defend on ground of casus but not of fire, sec 327.

When there is an alternative still open, impossibility does not exist, sec 328.

Bond with an impossible condition is void, sec 329. Partial impossibility abates pro tanto, sec 330.

Impossibility may be permanent or temporary, sec 331.

Sec 296

Impossibility may be either original or subsequent; the first being when the impossibility existed at the time of the making of the contract, the second coming into existence subsequent to that period. Original impossibility may be either objective or subjective; the first being where the thing which is the object of the contract is not capable of being done; the second where the parties are incapable of doing such thing. Original impossibility, also, may be either temporary or permanent; and may be partial or absolute.1 As will be hereafter more fully seen, temporary necessity only temporarily suspends the remedy,2 and partial necessity only abates pro tanto3