In response to Socrates's claim that he wishes another to give advice before he does himself, Nicias gives his opinion that the art of practicing fighting in armor is useful to young men. Nicias argues that it is to the advantage of youth to practice any art that gives them bodily exercise rather than rest. Furthermore, when a line breaks in battle, a person who is practiced in the art of fighting in armor will be better equipped to defend himself against assailants and will be less likely to sustain harm. Also, Nicias argues that the learning of the one art will inspire a boy to learn others such as "the proper arrangement of an army."
From this, Nicias argues that the boy's ambition will be fired and he will wish to continue a courageous career in warfare. Therefore, according to Nicias, the art of fighting in armor should be taught to the young men. Laches replies with skepticism. He claims that he would not say that any kind of knowledge should not be learned, because all knowledge appears to be good. He then states that the use of arms is really a kind of knowledge, as Nicias has described it, and as such it indeed should be taught to all young men.
However, Laches says that the people who teach fighting might be deceivers and that it may not constitute knowledge at all. Laches questions the value of the art of fighting in armor by pointing out that "the Lacedemonians, whose whole life is passed in finding out and practicing the arts which give them an advantage over other nations in war" have not adopted the method of fighting in armor. Laches further attacks the value of fighting in armor by stating that of all the men he has met who practice the art of fighting in armor, not one of them has ever been distinguished in war. Laches then goes to relate a story about a man named Stesilaus, a teacher of the art of fighting in armor. Laches claims that although Stesilaus appears to teach and practice fighting well, he is so poor a fighter in actual battle that all of his companions laugh at him for his ineptitude. Laches claims that in his own experience the character of such men fighting in armor has most often seemed cowardly, and thus the art is not worth the trouble for the youths.
In this section, Laches and Nicias each gives his own expert opinion on what he thinks is the right thing for Lysimachus and Melesias to do with their children. Nicias's view is somewhat simpler than the position Laches takes. Nicias seems to take it for granted that any kind of knowledge, as long as it is knowledge, is good and valuable. Therefore, Nicias assumes that knowledge of fighting in armor must also be good and valuable. Laches accepts that all knowledge is good because there is no such thing as bad knowledge. He does, however, disagree with Nicias's implicit claim that all knowledge is valuable.
This distinction between goodness and value is typical of the optimism of much of Plato's thought and much of Greek thought in general. To Plato, all knowledge, as long as it was knowledge, was to be set on the highest level of goodness. This is why Laches, even though he goes on to argue that the art of fighting in armor is entirely useless, still maintains that this useless knowledge is good, simply because it is knowledge.
Nicias also emphasizes another key theme of the Laches—that one cannot trust a teacher who is not a shining example of what he himself teaches. By describing the example of Stesilaus, Nicias brings up the possibility of different kinds of useful and useless knowledge. Although this teacher of the art of fighting in armor claims to be very knowledgeable in his art, the question is raised as to what kind of knowledge he possesses if it is not the kind of knowledge that allows him to succeed in battle. Although he may have knowledge of a sort, it seems a very different kind of knowledge than the kind that Nicias and Laches must have had to succeed honorably in battle. The knowledge of Stesilaus, if we wish to call it knowledge at all, seems a much more useless knowledge for a young man who wishes to learn how to succeed in battle. By stating that the art of fighting in armor is the only art in which the experts are poor practitioners, Nicias separates the art of fighting in armor from other arts as a kind of art with no practical use. Furthermore, Nicias re-emphasizes the connection between knowledge and experience by insisting that his knowledge of the men who practice the art of fighting in armor is based on his own experience of such men in battle.