Gemara :


Ein Ayah: The heretics are mistaken when they say that the main goal is the spirit of the Torah, in other words, its true ideas and the good moral attributes that it promotes. Based on this, they distinguish between that which they consider central philosophical themes and other stories and mitzvot. However, they are very mistaken for thinking that the philosophical ideas are already the final goal. In truth, the goal of human shleimut (completeness) is truly achieved when one can live and act, both on a general and on a specific basis, based on these philosophies and the good attributes seen through the Torah. To accomplish this, one needs all of the matters of the Torah, which make the entire nation used to a proper approach to life.
When even a small part of the Torah is not followed in practice, the philosophies will remain as an independent thing, and life will run as according to a person’s desires and whims. Under such circumstances, even the more general ideas of the Torah will, Heaven forbid, be undone. They will not succeed in having part of the Torah, as Hashem, whose word stands forever, instructed how success must be reached.
It is heretics who rail against the practical mitzvot, which incorrectly seem to them as a burden and unnecessary because they see the philosophical side as the main thing. However, this is a mistake because the actions all direct a person generally and specifically toward a path of life. When one’s specific actions are not delineated based on the Hashem’s Torah, the ideas cannot play their role at all. As time goes on, opposition to the proper ideals will increase, based on the habit of actions that the individual chooses. These random actions are antithetical to the pure ideals, and thus the philosophical idealism will be forgotten over time and nothing of them will last. Only about those who follow the Torah does it say "And this is My covenant with them, said Hashem: My spirit that is upon you and My word that I put into your mouth will not stray from your mouth and the mouth of your offspring and the mouth of your offspring’s offspring, said Hashem, from now and forever" (Yeshaya 59:21). The spirit refers to the general spirit of the Torah; the word refers to the specific required actions. When they are followed in detail, then they will not stray from your mouth, referring to those things that need to be pronounced with the mouth because the heart does not remember them by themselves like those things that are "My spirit that is upon you." Under such cases, there is an eternal covenant of "from now and forever."