We find in Parshas Yisro the most momentous occasion in the history of the universe. It happened during the month of Sivan that the Jewish people, every man, woman and child, heard Hashem Himself communicate the Aseres HaDibros. It is the first of the Aseres HaDibros, stating "I am Hashem your G-d" (שמות כ':ב'), that expresses the most essential belief: belief in Hashem's existence, belief that G-d is real.
The Rambam, in his Sefer HaMitzvos (מצות עשה א'), derives from that first utterance what he counts as the first of the Taryag Mitzvos, to believe in Hashem. Actually, however, there seems to be a bit of a discrepancy in the words of the Rambam. In the Sefer HaMitzvos (שם), he says that the Mitzvah is to believe in Hashem, while the wording in his Mishneh Torah (פרק א' מהל' יסודי התורה הלכה א') indicates that the requirement is that one should know that there is a G-d. Such discrepancies in the Rambam are, of course, not to be treated lightly; there must be a lesson here.
Rav Noach Weinberg has suggested that the Rambam is telling us the minimum and maximum requirements of this Mitzvah. Of course one must believe in Hashem. But a Jew must at least attempt to acquire the evidence necessary to believe in Hashem, as opposed to taking a mere emotional leap into blind faith. Ultimately, one must strive for the clarity indicative of knowledge, and the unadulterated evidence that would allow one to be absolutely sure about Hashem's existence. The Rambam thus assures us that attaining this knowledge is a feasible and readily available goal, and all one has to do is observe the wonders that occur to us daily.
The question is, though, why we are not all walking around in a state of bliss with the absolute knowledge of Hashem. The answer to this seems to be that we are not connecting to the straight-forward message that surrounds us all in a straight-
forward manner. Our desires seem to be blocking the truth. Rav Elchanan Wasserman, in his קובץ מאמרים, explains why Chazal say that the imperative "ולא תתורו אחרי לבבכם," "do not stray after your hearts" (במדבר ט"ו:ל"ט), refers to מינות, or false beliefs. After all, he asks, aren't beliefs in the domain of the mind? Why would the Torah speak about the heart? He suggests that this is because it is the desires of our hearts which often determine our intellectual stand on various issues. The truth is available, but only for those who proceed straight, careful to avoid the twists and turns dictated by the heart. Avraham Avinu, in his discovery of monotheism, was a naturalist; he was simply connecting to the events around him in a normal and straight- forward manner. He thus saw Hashem and His Mitzvos where others saw other things.
It is said that from the heart to the mind is a short distance, meaning that we're often quick to form philosophies that sanction our desires. The journey from the mind, from that which we truly know to be right, onwards to the heart, however, can be an infinite journey. The study of Torah is the power that helps us to stay on course, and will help us to realize that all we really want is what we really knew all along, that "אנכי ה' אלקיך," meaning that Hashem is our G-d.