Philo Judaeus De Fuga Et Inventione 27

[27] Do you not know, that if a man unacquainted with navigation, takes the management of a ship, which might otherwise have reached the harbour in safety, he overturns it? but that a man, skilful as a pilot, has often saved a ship which otherwise must have been lost? And also, some sick persons, owing to the unskilfulness of their medical attendants, have been severely afflicted with disease; while others, through the skill of their doctors, have escaped from dangerous sicknesses? And why need I have been prolix on this point; for always the things which are done with skill, are a conviction of those which are done unskilfully; and the true praise of the one is an unerring accusation of the other.