Plutarch Quaestiones Convivales 2.7.2

[2] Then said I: This is a mere shift and avoiding of the question, rather than a declaration of the cause; but if we please to consider, we shall find a great many accidents that are only consequents of the effect to be unjustly esteemed the causes of it; as for instance, if we should fancy that by the blossoming of the chaste-tree the fruit of the vine is ripened; because this is a common saying, or that the little protuberances in the candle-snuff thicken the air and make it cloudy; or the hookedness of the nails is the cause and not an accident consequential to an internal ulcer. Therefore as those things mentioned are but consequents to the effect, though proceeding from one and the same cause, so one and the same cause stops the ship, and joins the echeneis to it; for the ship continuing dry, not yet made heavy by the moisture soaking into the wood, it is probable that it glides lightly, and as long as it is clean, easily cuts the waves; but when it is thoroughly soaked, when weeds, ooze, and filth stick upon its sides, the stroke of the ship is more obtuse and weak; and the water, coming upon this clammy matter, doth not so easily part from it; and this is the reason why they usually scrape the sides of their ships. Now it is likely that the echeneis in this case, sticking upon the clammy matter, is not thought an accidental consequent to this cause, but the very cause itself.