Lets Use Our Heads
When the Torah describes the crimes of the generation of the flood it says that they were guilty of idol worship, promiscuity, murder, and 'chamas'. Rashi translates chamas as robbery. It was this crime that ultimately singled this generation beyond all the previous generations for the flood. So one can ask how is robbery worse than idol worship? Promiscuity? Murder?
The Maharal answers that for all the other crimes a bit of spirituality is required to understand why they are wrong. But to know that robbery is wrong requires only sense, "sechel." It is common sense that society can not prosper if robbery dominates. Because they didn't even follow their sense that G-d could find no good in the generation except for Noah.
But one could ask, why is rebelling against my imperfect sechel worse than rebelling against the almighty? One would think that it would be the opposite. To understand this I'd like to move from the beginning of time to the end of time. There is a very difficult, confusing, and famous gemara at the end of Sotah. It talks about the generation just before the Messiah comes. We can see much of what they say in our own times. This generation, it says, will be filled with chutzpa. At this time people who should not speak will be speaking. The people who should be speaking (for example the talmid chachamim will be silent. The wisdom of the wise will stink. The great will rise for the small, and the small will sit before the great. Those who fear sin will be derided as fools. The generation will have the face of a dog. At this time, the gemara states, our only hope will be G-d.
One might ask about this gemara, who else could we depend on anyway? Haven't we always depended on G-d. The answer is that we always have quite a lot to depend on. We have our scholars, and the way of our neighbors. We have what we can observe from the respected members of the community. Thus we can rely on our sechel. But this generation will have everything topsy-turvy. The great will look small and the small great. There will be no sechel. This generation can only look to G-d and hope that he who protects fools will not let us stray too far from the path.
A tragedy that points out the importance of sechel occurred near the peak of history. It is the the tragedy of Nadiv and Avihu, Aaron's sons. The Torah does not explicitly state what they did wrong in their service they were consumed. But the Talmud states that they were drunk when they came before G-d with their sacrifices. But one can ask the prohibition on service while drunk only occurs in the next episode. At this point there was no such prohibition. But the answer is where was their sechel? It should be obvious that to come before G-d, to enter the mishkan, to enter the Holy of Holies, you don't go there drunk! Well obviously it wasn't so the next parsha places a prohibition on doing the service drunk. Similarly Avraham, Yitzhak, and Yaakov were able to follow the whole Torah just with sechel. Its only when we could no longer follow through sechel did we receive the physical Torah.
Sechel is the tool the almighty gave us to serve him. Ignoring this gift makes sensible service impossible. Discarding our sechel is thus the greatest of crimes we as a generation can commit.