Hayom Yom: Tevet 20

See Tanya chapters 1 and 2 for an introduction to the concept of two souls. In our context the point is this: Each Divine soul (neshama) desires not only that the person himself fulfill G‑d's Will (to study Torah and be active in avoda) but also desires that another do so. Selfless concern for another's spiritual welfare is, after all, part of the basic "goodness" and character of the neshama. By contrast, the hedonistic natural soul is basically self-centered; it is not driven by a desire that another should enjoy physical pleasures etc. So, when two Jews study Torah together, the natural soul within each of them attempts to hinder that person alone. The G‑dly soul, however, since it also desires the other's welfare, joins forces with his neshama, so that "...there are two Divine souls against one natural soul."