Rabbi Steinsaltz writes:
A person who is capable of Torah study, idle chatter is not a permissible mundane act but a prohibition.
The Talmud expresses itself is quite vehemently, interpreting the verse “those who forsake God shall perish” as referring to those who leave the books of Torah and go out.
This is not just an act of omission, a failure to do something, but rather an act of commission, an active abandonment of the Torah
But severe penalties are meted out for neglect of the Torah in particular, apart from the general retribution for the neglect of a positive commandment through indolence, namely, in the “Gehenna of snow,” as is explained elsewhere.
The assumption is that a person who is able to study Torah and does something else instead acts out of laziness, and the punishment for laziness is the “Gehenna of snow.”
There are two types of Gehenna (Hell): one of fire (intense heat) and one of snow (intense cold).
The Gehenna of fire is the punishment for possessing too much ardor, for having wanted too much, having done too much, and having pursued what one should not have pursued.
The Gehenna of snow is the punishment for not possessing enough ardor, for not having desired, not having done, and not having pursued all the mitzvot that one ought to have desired, done, and pursued.
Likewise, one who occupies himself with the sciences of the nations of the world, this is considered as “idle chatter” insofar as the sin of neglecting the Torah is concerned,
The sin of neglect of Torah is so severe that what a person does instead, whether nonsense or profound intellectual study, does not make any difference.
There is no real difference between discussing the price of shoes and delving into philosophy, if it is in place of the pursuit of Torah.
–Rabi Adin Steinsaltz