IMPOSSIBILITY

In Roman law, as in ours, agreements for plain impossibilities, or on conditions involving plain impossibilities, are void, though, naturally, many things quite possible to us were thought of as impossible in Rome. There are some points of terminology which should be mentioned. Augustan and earlier Latin had no such word as impossibilis. Labeo has to express the idea in Greek, and Julian does the same, though by his time the word impossibilis had acquired citizenship. It never seems to have been very common. The more usual expression is ‘in rerum natura non esse’ or the like, in which the influence of Greek philosophy is evident. Though texts not infrequently use the word impossibilis without limitation to any particular type of what we should call impossibility, it does not seem ever to be specifically applied except to something to be done or given. To touch the sky with one's finger is impossible: that a son should be older than his father is still contra rerum naturam.

The rule laid down in the most general terms, ‘impossibilium nulla obligatio est’, and covering legal impossibility as well as physical, seems to apply in practice in our own law, though on the last application there is little authority. With us the line taken seems rather to be that the parties must have assumed possibility as the basis of the contract, so that it is theoretically, and perhaps practically, possible for a man to contract validly to perform an absolute impossibility.