1) Abaye's opinion is that a Listim Mezuyan is a Gazlan. One is never expected to be able to defend property against an armed robber. This is an "Ones" -- the money was stolen in a totally forced way. The Hagahos Mordechai (#206, printed at the end of the Mordechai at the back of the Gemara) writes that according to the opinion that Listim Mezuyan is a Gazlan, this also means that any Genevah done through an Ones, in a forced way, is classified as a Gazlan. We learn this from the opinion of Abaye, because the Listim Mezuyan hides away from people wherever possible and always tries to carry out his thefts in secret, but he is still called a Gazlan. It all depends on whether or not it was an Ones. The Hagahos Mordechai writes that the only difference between Abaye and Rav Yosef is whether the robber through Ones has to pay Kefel. According to Abaye, he does not pay Kefel, since he is classified as a Gazlan, while according to Rav Yosef he does pay Kefel since he is classified as a Ganav. However, a Shomer Sachar will always be exempt, both according to Abaye and Rav Yosef, since there is no way he can be expected to prevent the theft even though he is a paid watchman.

2) The Gemara below (79b) tells us that a Gazlan is somebody like Benayahu ben Yehoyada who "robbed the spear from the hand of the Mitzri." A Gazlan does everything openly. Rav Yosef says that a Listim Mezuyan is different. The Rambam (Hilchos Genevah 1:3) writes that even though the owners know that the theft is taking place, since it is not being carried out openly he is classified as a Ganav. Since the armed robber tries to hide from people if possible, this means he is not behaving like a typical Gazlan.

To summarize, according to Abaye, a Listim Mezuyan is a Gazlan since the act is totally forced, while according to Rav Yosef he is a Ganav because he tries to do it in secret.

3) I saw an explanation by the Lechem Mishneh (on the Rambam, Hilchos Genevah 1:3) for the dispute between Abaye and Rav Yosef. This seems more straightforward than the explanation that I gave above.

a) The Lechem Mishneh writes that the opinion (Rav Yosef) which maintains that the armed robber is a Ganav looks at the action that the robber carries out. He behaves like a Ganav, since the definition of a Ganav is somebody who does his stealing in a secretive way. Even though the owner saw what he was doing, and the reason he did not try to resist is because he knows that the thief carries arms, since the action which was carried out was done quietly it is classified as a Ganav.

b) The opinion which maintains that a Listim Mezuyan is a Gazlan (Abaye) looks at things differently. If the victim of the armed robber decides to try and resist, the robber is prepared to get violent. He is armed and prepared to kill, or at least inflict significant wounds. Therefore, he is classified as a Gazlan, because even though it is quite possible that the victim might not even know about the robber since he does things so quietly, on the other hand we must consider what the Listim Mezuyan is prepared to do if necessary.

c) I would add a small thought to what is stated by the Lechem Mishneh. The Listim Mezuyan may appear to be a quiet individual, but his strength lies in the fact that he is well-armed. He does not want to use his arms if at all possible, but on the other hand his danger is that he is quite capable of using the weapons, and this is his key to "success" as a bandit.

d) To summarize, we may say that according to the Lechem Mishneh, Rav Yosef looks at the beginning of the act, while Abaye looks at the end. Rav Yosef says that he is a Ganav because he starts off as a quiet, secretive Ganav, and Abaye says he is a Gazlan because he is prepared to finish his activity with violence.

Kol Tuv,

Dovid Bloom