אם יאמר לך אדם: יש חכמה בגוים - תאמן... (ואם יאמר לך אדם) יש תורה
בגוים - אל תאמן
מדרש איכה רבה פרשה ב סימן יג
If someone tells you there is wisdom among the nations - believe them. (If someone tells you) there is Torah among the nations - do not believe them.
The Midrash draws the distinction between Torah and Chachma (wisdom), in that wisdom can be found among all the nations, but Torah is only found among the Jews. But how exactly is Torah defined such that we can says it is something that is found only among the Jews?
A further question: Chazal say:
אם אין יראה אין חכמה
משנה אבות ג יז
If there is no fear, there is no wisdom.
We just said wisdom is something that can be found among the nations, how can we now say that wisdom cannot exist without fear? Are we to believe that all the scientists and thinkers of the world are G-d fearing people?
Perhaps the following understanding can answer these questions:
When Chazal say that if there is no fear, there is no wisdom - they are not necessarily referring to fear of G-d, but rather any fear. Wisdom is always an outgrowth of fear. In order to have something wise to say on any topic, one must be afraid of the repercussions of being wrong. In as much as someone is not afraid of being wrong, there is little motivation for them to think deeply or correctly. For scientists, this may come in the form of peer review of their work, or their fear of damaging their reputation, or their fear of failure. For businessmen, this may come in the form of fear of losing their money or missing out on big deals. In cases like these, Chazal say that you can trust their wisdom, provided that there is some fear behind it. (This is evident from the fact that Chazal will trust a non-Jewish chef to taste to see if a non-kosher ingredient has fallen into a pot of food, since he is afraid that his reputation is on the line if he gets it wrong.)
When it comes to Torah, however, the motivating fear is fear of G-d. One's insight in Torah is only worth as much as they have fear that one day they will stand in front of their creator and have to justify their actions and their reasoning behind their decisions.
Often secular wisdom is necessary in order to keep the Torah properly and make correct decisions. In these instances, one's learning the secular subject may be motivated by the fear of one day standing in front of G-d and needing to justify one's actions. In this case, that secular wisdom may be considered Torah in as much it is motivated by fear of G-d, like in the Rambam's case. Greta Thunberg, on the other hand, is likely not motivated by fear of G-d, but rather fear of climate change, which would put her squarely in the realm of Wisdom and not Torah.
On the other hand, one may develop insights in Torah, not based on fear of G-d, but rather because of fear of losing their reputation in the Jewish community. In this case, perhaps it would not be called Torah, but rather merely wisdom.
According to this, the Bracha that you make on a Torah Scholar is particularly apropos: שחלק מחכמתו ליראיו
Torah is the wisdom which is an outgrowth of fear of G-d, as opposed to other wisdom which is the outgrowth of other fears.