That great contemporary doctor Vindicianus was consulted by someone and he prescribe a remedy for a sickness that seemed suitable at that time. The man used it and was restored to health. A few years later his physical complaint flared up again. He decided to apply the same remedy. His health deteriorated further. He was surprised, and hurried back to the doctor to tell him what had happened. Vincidianus, a very clever man, replied, ‘the reason that you are responding badly to this is that I did not prescribe it.’ As a result, all those listeners who did not know him well thought that he didn’t rely on his medical skill but on some forbidden powers. Later on, when some of those who had been amazed by him questioned him, he explained to them what they hadn’t understood: he would not have prescribed that remedy for a man of that age. A remedy is only effective if it alters in accordance with different ages following a system of expertise that does not change.

The claim that what was once correct action can never be altered is, therefore, untrue. Rather, when the circumstances of time have altered, true reason normally demands that actions that were previously correct now be altered. Consequently while they argue that an action can’t be correct if it is altered, truth, by contrast, proclaims that the action will only be correct if it changes; each action will be correct precisely when it is adapted to each different period of time. The same may hold of different persons during the same period.

augustine, letter to marcellinus (411/412), pp.31-32

dad's only been saying this for like 15 years. but all the same, this is awesome. AWESOME.