Differing definitions of friendship: “people who hang out together”, “people who just get along”, “share each other’s interests”, etc. Rather than friendship, I would classify these explanations under what Karol Wojtyla called in Love and Responsibility: “sympathy”. Sympathy certainly has a place in many relationships, but it is not true friendship.
Wojtyla draws his definition of friendship unmistakably from St. Thomas Aquinas. While sympathy plays an initial and later supplemental role in fostering friendship, it is ultimately the will according to Wojtyla and Aquinas which sustains friendship. Even more specifically, the will as gifted with hope in turn provides for true friendship. Placed in sequence then, ideal friendship between persons runs this course:
Sympathy→ Conformity of Wills → Virtue of Hope
Far too often today, “friendship” remains on the sentimental and sympathetic level. And unfortunately, Wojtyla indicates in romantic relationships especially, “As soon as sympathy breaks down they often feel that love too has come to an end”. Yet, the other danger, in which Wojtyla seems to differ from Aquinas, is that when friendship grows cold it must be supplemented by sympathy. As in the case with marriage, a “union of wills” does not necessarily provide for a successfully long-term relationship. Likewise, Daniel Schwartz notes about Aquinas’ view of friendship that the virtue of hope must be active in addition to “conformity of wills”.
The necessity of sympathy is a given as it fosters many relationships anyway, strictly based on “subjective intensity” of encounter with another. Hope, on the other hand, does not reveal itself as necessary until the temptation towards distrust begins to creep into relationships. That is to say,
uncertainty about what a friend or potential friend wants and desires can be an obstacle to friendship. And the same goes for certain sorts of uncertainty about what a friend will want and desire in the future. In chapter five Schwartz discusses, first, Aquinas's view that we should presume good of others, unless there be evidence to the contrary, and hence that we should presume that people mean what they say, other things being equal and unless there be evidence to the contrary. (Schwartz calls this a ‘presumption of authenticity’.) Second, Schwartz tries to show how hope, for Aquinas, can be an aid to friendship, by being a cause of friendship, by sustaining friendship, and by warding off the ‘destructive social impact of despair’.
So again, Wojtyla appears to differ from Aquinas in this respect by supplying sympathy as a ‘cause’ of friendship while Aquinas supplies ‘hope’. But as I have indicated elsewhere, St. Thomas Aquinas does not exclude emotions from the dynamism of love as many suppose he does! Rather, Aquinas’ proposal of hope as crucial to sustaining friendship includes the emotions and sympathy just as Wojtyla would not exclude the virtue of hope either. The following sequence continues to apply to both Wojtyla and Aquinas’ view, though I would note a supplement of sympathy moreso in Wojtyla’s approach:
Sympathy→ Conformity of Wills (& Sympathy) → Virtue of Hope (& Sympathy)
This sequence would readily agree with Pope Francis’ more recent insistence on the necessity of tenderness in relationships, or more aptly named “mercy” which Aquinas deemed as God’s most potent attribute!
 Wojtyla, Karol. Love and Responsibility. “From Sympathy to Friendship” 88-94ff Ignatius: San Francisco, 1981.
 Aquinas’ own definition surprisingly differed from Aristotle’s: Justice was essential to Aquinas’ view of friendship whereas to Aristotle, ‘when men are friends they have no need of justice’ (Nicomachean Ethics 1155a 26).
 Ibid, 90. See also Wojtyla’s ‘Libidinistic’ Interpretation (61).
 Ibid, 91. See also Wojtyla’s ‘Rigorist’ Interpretation (57). Pope Francis has also termed sympathy as ‘tenderness’.
 Daniel Schwartz, Aquinas on Friendship, Oxford University Press, 2007, 189pp.,
 Wojtyla, Karol. Love and Responsibility. “From Sympathy to Friendship” 90
 Michael Rota, University of St. Thomas reviews: Daniel Schwartz, Aquinas on Friendship, Oxford University Press, 2007, 189pp.
Although originally 2 different posts I have combined these under common theme
A group of friends drawn initially together by the philosophy of Edmund Husserl, included: Max Scheler, Edith Stein, Hedwig Martius, and Roman Ingarden. There were many more great minds in the following of Husserl (including Heidegger and Von Hildebrand) but I find the relationships of these four significant on the feast of St. Teresa Benedicta of the Cross because of the effect that they had on the person of Edith Stein and her legacy.
Max Scheler, for his part, is credited by lecturer Benjamin Gibbs as having empowered Stein “to take religious ideas and attitudes seriously for the first time since her adolescence” In Stein's own words, Max Scheler had almost mythic status:
One’s first impression of Scheler was fascination. I have never encountered the phenomenon of genius so clearly in any other person. His large blue eyes seemed to radiate the light of amore exalted world. His features were handsome and noble; yet life had left some devastating traces in his face.
It's interesting to note, that Husserl and Scheler authored philosophical works which provided an alternative to 'psychologism' or the scientific pretentions of psychology. Since Freud's work would have been popularly widespread in their day, I can only guess as to why they would be formulating a much more sound phenomenology than the be-all/end-all discipline of psychoanalysis. I have written elsewhere of Scheler’s refutation of psychology and was unaware that this was also one of Husserl’s tenants of Phenomenology. Indeed, Gibbs notes that this point was one of the first things that drew Stein to Husserl. Gibbs notes, “Edith studied psychology at Breslau University for four semesters. By then she had become discontented with psychology’s lack of a scientific basis” What is meant by “science” here is simply an ordered, logical basis in accord with reality. Something she found much more apparent in Husserl’s Logical Investigations.
Besides Scheler, Stein found lifelong friends in Hedwig Martius (later Conrad-Martius), Roman Ingarden and Adolf Reinach (and his wife Anne). Though Hedwig decided to convert to Lutheranism, it was in her family library that Edith found the Life of St. Teresa of Avila. Famously, though the exact details are lacking, Edith’s own words relate:
For twelve years Carmel had been my goal, since the summer of 1921 when the Life of our holy mother Teresa came into my hands and put an end to my long search for the true faith.
Her friend Roman Ingarden, a Polish philosopher from Krakow, would later become a teacher of Karol Wojtyla. The two friends corresponded about numerous topics, both philosophical and personal. Gibbs notes that both Ingarden and another professor named Hans Lipps may have been romantic interests for Stein,
According to Hedwig Conrad-Martius – Edith’s philosophical colleague and friend Hans Lipps. But her love for him was not reciprocated; at least, it was evident that Lipps didn’t want to marry her. Another object of Edith’s affections may have been Roman Ingarden, to whom she wrote over 150 letters, mostly reporting the details of her work with Husserl. In one letter Edith addressed Ingarden as ‘Mein Liebling’ – ‘my dear’. But he returned to Poland early in 1918 and married a school doctor the following year. Edith wrote congratulating him on his marriage, and asked him to burn any personal letters from her that he might have kept.
Roman Ingarden would have been the teacher to relay Max Scheler to the young Karol Wojtyla in Poland. Gibbs notes, “The future Pope wrote his Habilitationsschrift on the ethical theory of Max Scheler”. Through Ingarden as well, Wojtyla must have been introduced to the person and though of Stein. He too would later canonize her as St. Teresa Benedicta of the Cross.
It’s fascinating to trace how the friendships that arose from the initial followers of Husserl made a tremendous impact on history, even to the degree that Karol Wojtyla would adopt much of the thought of the Phenomenologists. However, a sad note is the subsequent break of Husserl with his students as he distanced himself especially from Stein on account of her being an ambitious woman in a “male profession”. His own thought became more and more disjointed, whereas his students carried the integrity of the Göttingen school far beyond his reach.
Benjamin Gibbs study of Edith Steins life, to which I refer often here, does not claim to cover the entirety of her story and makes no mention of her sister Rose’s journey to Carmel with her. What he intended to do was to collect previously untranslated German letters of Stein, as well as include her unfinished Autobiography, Life in a Jewish Family, as major sources in the corpus of Stein’s life (because only the popular but imprecise memoir of Teresa Benedicta as written by Sr Teresia Renata Posselt was available as yet). He does well to fill and blanks in her life, and I thoroughly enjoyed seeing the network of philosophers who influenced her ultimately toward Catholicism.
A final note regarding Stein's "friendship" with Husserl. It lacked "sympathy", even though Stein herself attempted to reconcile "empathy" with Husserl's discipline in her own painstaking work on the subject. Their relationship only reflected the "conformity of wills" aspect of the following sequence (although the conformity of Husserl's will is questionable):
Sympathy→ Conformity of Wills → Virtue of Hope
Indeed she often refers to him as "the master", which unfortunately reveals a master/slave dynamic at work, especially since he would not allow her to become his peer professionally and kept her at the level of secretary.
On the other hand, her longstanding friendships e.g. Roman Ingarden did reflect this sequence:
Sympathy→ Conformity of Wills (& Sympathy) → Virtue of Hope (& Sympathy),
and she found that they too disagreed with Husserl. Her work with empathy turned out to be the last scholarly chance for Husserl to change his thinking, and unfortunately he did not.
 Gibbs, Benjamin. ‘My long search for the true faith’: The Conversion of Edith Stein. www.carmelite.org/documents/Heritage/gibbsconversionofstein.pdf, May 2012 p.12. It's important to note also that Gibbs mentions often how Stein was not an atheistic philosopher in principle, she merely 'stopped praying' at one point in her young life, and she did not begin again until interacting with brilliant philosophers in Gottingen, Germany.
 Stein, Edith. Life in a Jewish Family, An Autobiography. translated by Josephine Koeppel, OCD. http://www.sistersofcarmel.com/edith-stein-life-in-a-jewish-family/ 1933
 Gibbs, Benjamin. ‘My long search for the true faith’: The Conversion of Edith Stein. www.carmelite.org/documents/Heritage/gibbsconversionofstein.pdf, May 2012 p.7. “For Edith, the attractive features of Husserl’s phenomenology were:(1) Husserl’s repudiation of the scientific pretensions of psychology, and of ‘psychologism’ -
the error of conflating the formal sciences of logic and pure mathematics with the empiricalmethods of psychology.” Psychologism is essentially the belief that psychology can explain all phenomena.
 Gibbs, Benjamin. ‘My long search for the true faith’: The Conversion of Edith Stein. P.6 Edith herself says, All my study of psychology had persuaded me that this science [phenomenology] was in its infancy; it still lacked clear basic concepts; furthermore, there was no one who could establish such an essential foundation. On the other hand, what I had learned about phenomenology so far fascinated me tremendously, because it consisted precisely of such a labour of clarification and because, here, one forged one’s own mental tools for the task at hand. (LJF 222)
 in die Hände gefallen war’. The translation in Posselt (2005) renders the German incorrectly as ‘had happened to fall into my hands’, thus appearing to support Posselt’s claim that Edith came across the book by chance. (ESGA I, 350; cf. Posselt 118).
 Gibbs: Letter of 1948 to Fr John Oesterreicher, in Never Forget, ed. W. Herbstrith (ICS 1998), 266.