The Importance of Group Learning

Gemara: "Hasket" (the word that begins the exhortation to be enthusiastic about learning Torah in Devarim 27:9) can be understood as follows: Break yourselves into groups for your learning, for Torah is acquired only as part of a group. This is as Rabbi Yossi bar Chanina said: The pasuk "a sword on the badim and they shall be shown as fools (v’no’alu)" (Yirmiya 50:36) is to be understood as follows. Scholars who sit as individuals (bad b’vad) as they are involved in Torah deserve a sword, and furthermore they become stupid, as it says here v’no’alu as it says elsewhere (Bamidbar 12:11), where it means to do something stupid. Furthermore, they will sin, as the same word is found in the context of sinning (ibid.).

Ein Ayah:The holy Torah is a blueprint of life that does not lead its followers to a life of abstinence from the pleasures of the physical world, as pleasures can raise a person’s personal level by bringing joy to his heart. Therefore, part of the characteristic of Torah is that it recognizes the need for a social life with friendships, which bring to the world a good life within society. This is particularly rewarding when one’s social group consists of good and scholarly people. Separation from other people and extreme asceticism, which is the approach of a significant portion of those people who, of their own, have sought closeness to Hashem, is a foreign idea to the Torah. For that reason, if one wants to acquire knowledge of Torah, he will succeed specifically by joining together with a group of learners, which shows the gains of avoiding isolation.
There are three main elements of danger when separating oneself from human interaction, especially for those who are involved in the world of philosophy and morality. Firstly one can be successful in improving the world through the ideas he studies only when his purity, fear of G-d, and understanding of Torah are accompanied by intellectual tolerance. It is crucial for the Torah thinker to deal openly with approaches to law, halacha, and even matters of morality that are different from his own viewpoint, so that he can fulfill "the truth and the peace shall you love" (Zecharia 8:19). This tolerance can only be achieved by a Torah scholar who studies Torah as part of a group and thereby becomes accustomed to different ways of thinking. Then he can see how the clear and straight approach is arrived at specifically by hearing a variety of scholarly views, in which the light of Hashem dwells.
When a person operates within a very narrow inner group and is unaware of a variety of people possessing logical but different approaches, he will not be able to stand viewpoints different from his own. This in turn is a strong cause of quarreling, which can bring to the "sword of discord" spreading throughout the nation, whether literally or figuratively. This unfortunate phenomenon starts from those who study Torah as individuals rather than study it with a spirit of "its sons/ its builders," as Chazal describe scholars who increase peace in the world (Berachot 64a).
The second problem of studying without a broad group is that the conclusions one arrives at are often wrong. Not only is the truth not attained intellectually, but the mistakes can cause one to sin in practice. Not only is a life of abstaining from permitted things a sin in and of itself (like a nazir who sins by forbidding wine upon himself), but a misguided rabbi can have a negative impact on society, if he does not arrive at clear conclusions, as is hinted at in one of the p’sukim the Rabbis cite in this context.