Socrates suggests that the conclusion just reached was "a shadow," and Menexenus asks him why (Menexenus continues to be the interlocutor here). Socrates again says that he is worried that their argument was false. "Arguments, like men," Socrates says, "are often predators." A friend, Socrates suggests, has a motive for friendship and an object in friendship. He then asks whether the object that makes a friend dear is itself dear or hateful to the befriender. This confuses Menexenus, and Socrates tries a different tack.
The sick man, Socrates says, is the friend of the physician because of disease (which is evil), and for the sake of health (which is good). The body, it has been concluded, is neither good nor evil. Thus, the friend (the body) is a friend for the sake of the friend (health) and because of the enemy (disease). Socrates suspects a fault here, and approaches it through another point. If medicine is dear for the sake of health, and health is dear for the sake of something else, and so on, there must be some "first principle of friendship or dearness" that lies at the end of this chain of reasons. Two examples are the father who values wine because it may cure his son of hemlock poisoning, and the man who values gold for some other purpose. Neither the wine nor the gold comprise what is truly valued.
That which is valued for the sake of something else, then, is not the truly dear. The same principle holds for friendship. If friendship is truly dear, then it is valued for its own sake: "the good is the friend." This is problematic, however, because, as Socrates has already suggested, the good is useless to us if there is no evil. Thus, it seems that good is valued because of evil. It would seem, if this were true, that friendships that are valued for the sake of something else would remain even after evil has gone, whereas true friendships, valued simply because they are good, would disappear.
This cannot be the case, however, as Socrates demonstrates with the example of hunger. Hunger may injure us or benefit us; it may be either good or evil. If evil disappears, then, we would still have hunger; it would simply be good or neutral hunger rather than bad hunger. When evil perishes, then, desires (inherently neither good nor bad) remain, and therefore so must love and friendship. If we accept this, then we cannot accept evil as the cause (or motivating factor) of friendship.
In this section of dialogue, Socrates dismantles the argument that previously constituted the strongest conclusion or resting-point in the Lysis (that friendship is caused by the neutral loving the good, motivated by the presence of evil). The overall concern with this prior argument is initially unclear: Socrates simply feels that it was a "shadow," and makes the further comment that "arguments, like men, are often predators." This last comment cuts straight to the intersection of philosophy and desire in the Lysis, and we will return to it in a moment.
Socrates develops an objection to his previous conclusion based on the new problem of receding causes. If someone is a friend for the sake of something else (as medicine is dear to the body for the sake of health), then we have not really arrived at the true principle of friendship; the true cause recedes back along a chain of intermediate causes. This objection shows Socrates's typical drive to find something that holds in all cases, and his relentless suspicion that any definition or comprehensive account is actually contingent on circumstances. The tension between this aim for a universal, self-contained definition on the one hand, and Socrates's constant use of specific analogies (like medicine) on the other, often accounts for the sense that the dialogue is not really getting anywhere. The trick is to find in a particular case (the father loves wine because it might cure his son) the element that is common to all such cases (someone loving something, and therefore a friend loving a friend).