
Book I, 1098a-b; §7 as translated by W. D. Ross
Nicomachean Ethics
Context: Let this serve as an outline of the good; for we must presumably first sketch it roughly, and then later fill in the details. But it would seem that any one is capable of carrying on and articulating what has once been well outlined, and that time is a good discoverer or partner in such a work; to which facts the advances of the arts are due; for any one can add what is lacking. And we must also remember what has been said before, and not look for precision in all things alike, but in each class of things such precision as accords with the subject-matter, and so much as is appropriate to the inquiry. For a carpenter and a geometer investigate the right angle in different ways; the former does so in so far as the right angle is useful for his work, while the latter inquires what it is or what sort of thing it is; for he is a spectator of the truth. We must act in the same way, then, in all other matters as well, that our main task may not be subordinated to minor questions. Nor must we demand the cause in all matters alike; it is enough in some cases that the fact be well established, as in the case of the first principles; the fact is the primary thing or first principle. Now of first principles we see some by induction, some by perception, some by a certain habituation, and others too in other ways. But each set of principles we must try to investigate in the natural way, and we must take pains to state them definitely, since they have a great influence on what follows. For the beginning is thought to be more than half of the whole, and many of the questions we ask are cleared up by it.

Book II, 1109a.27.
Variant translation: Anybody can become angry, that is easy; but to be angry with the right person, and to the right degree, and at the right time, for the right purpose, and in the right way, that is not within everybody's power and is not easy.
As quoted in The Child: At Home and School (1944) by Edith M. Leonard, Lillian E. Miles, and Catherine S. Van der Kar, p. 203
Nicomachean Ethics

“Without friends no one would choose to live, though he had all other goods.”
Book VIII, 1155a.5
Nicomachean Ethics
Source: The Nicomachean Ethics

“For the things we have to learn before we can do, we learn by doing.”
Book II, 1103a.33: Cited in: Oxford Dictionary of Scientific Quotations (2005), 21:9
Nicomachean Ethics
Source: The Nicomachean Ethics

Nicomachean Ethics
Source: Book I, 1098a-b; §7 as translated by W. D. Ross
Context: Let this serve as an outline of the good; for we must presumably first sketch it roughly, and then later fill in the details. But it would seem that any one is capable of carrying on and articulating what has once been well outlined, and that time is a good discoverer or partner in such a work; to which facts the advances of the arts are due; for any one can add what is lacking. And we must also remember what has been said before, and not look for precision in all things alike, but in each class of things such precision as accords with the subject-matter, and so much as is appropriate to the inquiry. For a carpenter and a geometer investigate the right angle in different ways; the former does so in so far as the right angle is useful for his work, while the latter inquires what it is or what sort of thing it is; for he is a spectator of the truth. We must act in the same way, then, in all other matters as well, that our main task may not be subordinated to minor questions. Nor must we demand the cause in all matters alike; it is enough in some cases that the fact be well established, as in the case of the first principles; the fact is the primary thing or first principle. Now of first principles we see some by induction, some by perception, some by a certain habituation, and others too in other ways. But each set of principles we must try to investigate in the natural way, and we must take pains to state them definitely, since they have a great influence on what follows. For the beginning is thought to be more than half of the whole, and many of the questions we ask are cleared up by it.

For one swallow does not make a summer, nor does one day; and so too one day, or a short time, does not make a man blessed and happy.
Book I, 1098a; §7 as translated by W. D. Ross
Variants:
One swallow does not a summer make.
As quoted in A History of Ancient Philosophy: From the Beginning to Augustine (1998) by Karsten Friis Johansen, p. 382
One swallow (they say) no Sommer doth make.
John Davies, in The Scourge of Folly (1611)
One swallow yet did never summer make.
As rendered by William Painter in Chaucer Newly Painted (1623)
One swallow does not make a spring, nor does one sunny day; similarly, one day or a short time does not make a man blessed and happy.
As translated in Philosophical Grounds of Rationality: Intentions, Categories, Ends (1988), by Richard E. Grandy and Richard Warner, p. 483
Nicomachean Ethics