In his translation of the Nicomachean Ethics, Joe Sachs notes that at IX.4 Aristotle turns away from the factors that cause certain relationships to fall short or fall apart and instead turns toward the central factors that unify the experience of philia. These include: loving someone for their own sake, wishing that they might have all good things in life, actually doing or giving some of those good things for them, wanting them to live and to live well, wishing to spend time together and share in the activities of life, valuing the same things, sharing in the joys and sorrows of life, etc.
Once again, Aristotle observes that mothers feel and do these things most of all; yet he further observes that the humane person who takes life seriously also feels and does these things with regard to himself. The reason is that such a person has internal agreement [homognōmonei = "knowing alike"] and consistently reaches out for the same things throughout life. This consistency is directed by his entire soul and is pursued for the sake of his thinking activity [nooun] or the thinking part of the soul [dianoētikos] - for this seems most of all to be a person and this most especially needs to be maintained and preserved (recall Aristotle's discussion in III.10-12 of sōphrosunē, which literally means "mind-keeping").
In IX.5 and IX.6, Aristotle discusses two of the main ingredients for close relationships: well-mindedness [eunoia, usually rendered "goodwill"] and like-mindedness [homonoia]. Note the connection between these terms and the Greek word for mind [nous]. It's almost as if those who are dear to each other share the same mind across two bodies. That's not really the case, of course; but according to Aristotle it is our mind and thoughts, including well-mindedness and like-mindedness, that figure centrally in love and friendship.
Like-mindedness is not the mere holding of similar opinions [homodoxia] about any arbitrary topic, such as one might find among scientists or co-religionists or political partisans. Instead, it involves having common goals, forming similar judgments, making similar choices, and acting on those choices together. This leads naturally to one of the most important aspects of philia: taking action for the sake of someone who is dear to you, which in VIII.6-8 he called the activity [energeia] of loving [philein] and which here he calls doing favors [euergetai, literally "well-acting"). It is through activity that we are what we are, and the person who acts well for the sake of someone they love creates something beautifully right [kalos] through this kind of activity (1168a10).
All of this shows that love [philia] is not only a feeling [pathos], but also a complete activity [energeia] and thriving [aretē] of the whole person. That's likely why Aristotle thought it was important to devote 20% of the Nicomachean Ethics to the topic.
(Cross-posted at philosopher.coach.)
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