E2P13C2
Corollary — Part II
Latin
Hinc sequitur corpus motum tamdiu moveri donec ab alio corpore ad quiescendum determinetur et corpus quiescens tamdiu etiam quiescere donec ab alio ad motum determinetur. Quod etiam per se notum est. Nam cum suppono corpus exempli gratia A quiescere nec ad alia corpora mota attendo, nihil de corpore A dicere potero nisi quod quiescat. Quod si postea contingat ut corpus A moveatur, id sane evenire non potuit ex eo quod quiescebat; ex eo enim nil aliud sequi poterat quam ut corpus A quiesceret. Si contra supponatur A moveri, quotiescunque ad A tantum attendimus, nihil de eodem affirmare poterimus nisi quod moveatur. Quod si postea contingat ut A quiescat, id sane evenire etiam non potuit ex motu quem habebat; ex motu enim nihil aliud sequi poterat quam ut A moveretur : contingit itaque a re quæ non erat in A nempe a causa externa a qua ad quiescendum determinatum fuit.
English (Elwes 1883)
(not aligned in this witness)
Modern English
From this it follows that a body in motion continues to move until it is determined to rest by another body, and that a body at rest continues to rest until it is determined to motion by another body. This is also self-evident. For suppose I take body A to be at rest and attend to no other bodies in motion: I can say nothing of A except that it is at rest. If it then happens that A moves, that cannot have come from the fact that it was at rest, for the only thing that could have followed from that was that A continued to rest. Conversely, suppose A is in motion: as long as I attend only to A I can affirm nothing of it except that it moves. If it then happens that A comes to rest, that too cannot have come from the motion it had, for the only thing that could have followed from the motion was that A continued to move. So it comes from something that was not in A, namely, from an external cause by which A was determined to rest.