I am the Lord your God, Who brought you out of the land of Egypt… (Exodus 20:2)
The first of the “Ten Commandments,” this verse raises the obvious question, “What kind of a commandment is ‘I am?’” (It’s less of a question in Hebrew, since “Aseres HaDibros” is more along the lines of “The Ten Statements,” though that would make a far less compelling title for a movie.) Nevertheless, this is a commandment. By metaphorically pointing to Himself and saying, “Look at Me,” God is commanding us to be aware of His existence. (The Talmud in Makkos 24a specifically calls “I am…” a mitzvah.)
You’ll notice that I prefer the term “to know that there’s a God” rather than “to believe in God.” When we know something, we accept it as an indisputable fact. When you believe something, it’s more a matter of opinion. For example, I may or may not believe that Kennedy was assassinated in a conspiracy. Maybe I’m right and maybe I’m wrong. In either case, it’s open to debate. However, I know that George Washington was the first president of the United States; if anyone tried to tell me otherwise, I would simply dismiss him out of hand. To suggest that Lincoln was the first president is silly and I’m not open to reconsidering my position on the matter. That’s how confident we should be that there’s a God Who created the world and is running the show.
The question is: how does one go about fulfilling the obligation to know that there’s a God? The evidence is all around us in this wonderful world He has given us! All we have to do is open ourselves up in every area of our experience, from botany to history – and, of course, Torah – and the proof of His being comes pouring in. (If not, then one must go out and look for it. But it’s there.)
Inherent in knowing that there’s a God is accepting the fact that we can never truly comprehend Him. The human mind is simply incapable of fully grasping the concept of the infinite, either in space or in time. We can say that we get it and spit back a definition, but as beings bound in a body, with a beginning and an end, we can never truly comprehend what it means to be without those limitations, like a person born without sight can never understand colors the way a sighted person does.
It goes without saying that we should not question His being just because we do not comprehend His actions. No matter how smart we may be, He is infinitely more so. By definition we cannot understand all that He does or we would be equally smart. Hey, I can’t even do calculus; how arrogant would it be for me to second-guess God?
The reason for this mitzvah is that it serves as the basis for absolutely everything else we do. If there were no God, everything else would be pretty meaningless.
This mitzvah applies to both men and women, at all times and in all places. In fact, it is one of the six “constant mitzvos” that never cease. A person could be laid up in bed for six months in a full-body cast (God forbid), but they could be fulfilling the obligation to know there’s a God every waking moment.
The obligation to know that there’s a God is codified in the Mishneh Torah in Hilchos Yesodei HaTorah. It is #1 of the 248 positive mitzvos in the Rambam’s Sefer HaMitzvos and also #1 of the 77 positive mitzvos that can be fulfilled today as listed in the Chofetz Chaim’s Sefer HaMitzvos HaKatzar.