As the Jewish people stood at mount Sinai and Moses descended holding two tablets, he also brought back with him 40 days of information. God chooses not to reveal himself to the world all the time. Sometimes, difficult things that seem terrible will happen and it will seem as thought God is not there. This lets us have such things as faith, and belief -virtues that would be impossible if we always saw God. But there was a time when God revealed himself to the world. He stepped into the land of Egypt and took out an opressed group of slaves, led them to mount Sinai, and revealed himself to them. He taught them the truth - that the is a Creator, and told them that it was their mission to teach the world about it. All of the civilized world accepts the Ten Commandments, for God revealed those to mankind. There was a total of 613 principles or ideas that God gave the Jewish people to make the world around them a better place. Those are called mitzvahs. Some teach us to be kind (charity, helping the oppressed) some teach us self control (kosher, do not steal) some teach us to be noble (save the life of the dying person.) Since God knows more about people than even the greatest psychologist, sometimes we must do what he says even if we don't really see how that mitzvah will help us.
Therefore, the very first thing that we must know is that somehow, and in some way ,the tefillin makes the Jewish man wearing them a better Jewish man, and makes the whole world around him a better world. Even if we didnt know any reason for it - we should do it - after all, how many of us know how Penicillin works, but we take it and it makes us better! There are many levels of depth and beauty to tefillin - i will try to explain two of them.
1) Tefillin wrapped on the arm and the head. We all have two parts to ourselves. We have our intelligence, and we have of physical bodies. A person who is trying to go on a diet sees the struggle between these two parts clearly. He sees a chocolate bar that he knows is unhealthy for him, and he decided that he had better not eat it. But someone he feels as though he wants it! His mind certainly does not want it. He will feel nothing but guilt should he eat it. And yet most of the time, diets fail. The body wins. This is true when a spouse cheats on the other spouse more often than not. The mind was saying "no" and the boys could not resist the temptation.
There are two parts to being a good person, and a good Jew. The first part it knowing right from wrong. If a person does not even know that his cholesterol is through the roof, he will not even know to lay off of the cheese doodles and Haagen-Dasz! Even after he knows this, however, he must still work to control himself, and teach his body to behave as his mind has decided. Life is about these two challenges. THe society that does not know that Murder is bad (like Jihad, or gladiator fights) is highly imperfect. But even a person whose mind does know still has much work left to do. Other religions say "Just believe in Jesus. Your faith will set you free." They do not stress Mitzvahs, for they think that only the mind counts. Other cult-ish religions stress only the actions, and tell you "stop thinking, listen only to the leader, and do what he says" Judaism tells us that we must tie down both our mind and our behavior to the Truth, to God. Our mind, and our body must be instruments of truth. If we have to choose between right and wrong, we should KNOW what is right and wrong, and the ACT accordingly. This is the measure of a great person. Tefillin are boxes with words of Truth, from the Torah inside, that speak of why were are here in this world. It tells about the Jew, his one God, his great mission in this world. Every morning, the Jew ties down his arm and head, (gently!) and says to himself, his God, and his world, "i will use my mental power and physical power toward noble goals - to make this world a better place." (on ancient times, people wore tefillin for the entire day - until the sun set! But this is almost unheard of anymore, although some great rabbis and others still do. The rest of us put them on for prayers once a day.)
2) There is another layer of meaning to tefillin too.. God is not physical. Just like you cannot ask someone to "Point to 'Love', what size is it what shape is it?" because love does not occupy a space, or have shape, the same is true for God. He is everywhere but he is not a body, or shape. Any yet, the Great Rabbi of 2000 years ago, recorded in the Talmud, tell us that "God also wears tefillin!" What does it say inside them? The talmud tells us that God's tefillin say "Who is like the Jewish people, a unique people on the earth." God has no body to put tefillin on. This is surely a story that is not meant to be taken as a description of what God wears. Here is the idea represented in tefillin. A young girl and boy fall in love, but he must go out to war. Before they depart, he gives her a locket - a little necklace with his picture on it, and she gives one to him. when they are separated, they each can look into that locket, and remember what they love above all. What the Jew loves above all is truth, Torah, and God. He has given his life throughout history rather than be forced to give up his Judiasm. The tefillin are the locket that a Jewish person wears that connect him to the one he loves, but is separate from - God. God loves us so much - we feel that when we wear tefillin. And God does not let us away from his heart for even a moment. It is almost as if "he is wearing tefillin." Not literally of course, but certainly true. There is no other nation in the world, in recorded history that has sacrificed everything again and again simply in order to remain true and good. From passover, to the Chanukah story, we have never given up our belief in one God who loves and cares no matter what anyone has tried to do to us. And they have tried it all. And yet, although the Jewish people have never done too much advertising, or PR, every single place that we have lived, the people have begun believing in one God. (Both Islam and Christianity got that part right) Everywhere that we did not live, those people are still bowing down to cows, and worshiping rivers. We are privileged to be of the people who are devoted Totally to God, and Truth. Our grandparents, and their grandparents stood for nothing more that doing everything that they could to be "God's people," of truth and love and honesty. And when they looked down at their tefillin, they knew that God had not forgotten them - just as the man at war knew when he felt the locket of his beloved fiance.