Here is a very informative response from a FB poster:
"Second sailing or second voyage" is an Ancient Greek sailing proverb; "when the wind fails, we use the oars." Plato uses the term in Phaedo 99d. He claims that the physicists were not able to satisfy him regarding the true causes of nature. He finds a clue in Anaxagoras' notion of mind (nous) and believes dialectic can take him the rest of the way. Hence, the move from the natural power of the wind to the artificial power of the oars. I think it is correct to characterize Epicureanism as rejecting the second voyage. Addressing Plato's concerns regarding the failure of the Physicist to explain adequately the causes of nature would surely have been one of Epicurus' key objectives.