For decades, the word was taboo. If you spoke it on the radio, they would blip it out. Only fundamentalist preachers, stirring the fear of the hell and damnation into their flock would use such a word in public. Or perhaps a vendor of perfumes, luring the darker side of its consumers.

But today, it's everywhere.

The word is 'evil'. As one commentator put it, on 9/11 the world had a moment of clarity. There, on the TV set, for all to see, was unadulterated, indismissible, raw evil. Moral relativism died at 2000º Fahrenheit.

But not so easy: Now that we're all allowed to use the word again, what is it?

Is it a real thing, with substance and power? Or is it no more than the absence of truth, a vacuum of reality, darkness, a negation of light? If it is real, then how could G‑d have allowed it in His world? But if it is only darkness, how is it possible for darkness to defy light?

No answer will satisfy us entirely. Evil is too close to us to see clearly; too painful to place a label upon. We feel that perhaps we are callously justifying the horrors that have befallen good people. Perhaps we are rationalizing G‑d — and ourselves — off the hook. But, on the other hand, without any grasp of what evil is, how can we be expected to fight it?

In Torah the metaphor for evil is darkness. No more than the absence of truth. A void of reality. Like darkness, Evil has no power of its own. From where, then, does it derive the power to cause so much pain in the world? Generally speaking, from us, from our fear of it. That we consider it a "something" worth negotiating.

With every spoonful of worry we foster it, with every glance of trepidation, every concession we make from our lives to acknowledge its threat — until Evil rises brazenly to attack us with our own instruments.

This theme is repeated throughout the Torah. When the snake approached Eve, the sages explain, she wasn't ready to give it the time of day. In her world, the snake might as well not even existed. So the snake had to say, "Is it true you're not allowed to eat from any of the trees in the garden?" Of course the snake knew this was a lie. But this way, Eve took notice of it. The snake became someone worth answering. And therefore, empowered to make a mess.

Similarly, Moses. Moses began his career as liberator when he killed an Egyptian taskmaster who was beating a Jewish slave to death. When he discovered that his deed had become public knowledge, the Torah tells us that "Moses was afraid. And Pharaoh sought to have him killed. So he fled" First Moses was afraid. Only then did Pharaoh seek to have him killed. Without Moses' fear, Pharaoh had no power.

All the more reason why 9/11 was our moment of clarity: Because we saw this no longer as an idea, but clearly acted out, a metaphor in action.

These people who wish to bring us down in terror, do they have any power of their own? Do they have resources that can feed a populace? Ideas that can thrust them ahead of our progress? Do they attack us with missiles of their own device and engineering?

No. They have nothing of their own. They were empowered by us through the bizarre machinations of Cold War politics. They wield razor blades bought in our hardware stores, and with them they hijack airplanes we devised to better our standard of life. They strike fear in our hearts with powder stolen from our laboratories. Dust. Knowing full well they cannot infect a nation. But they can get us real scared. And for evil, that is already a victory. Because then, through our fear, evil has become real.

Knowing this is immensely useful. Once we have found evil's secret, we know how to deflate it. The strategy is almost identical, whether it be the evil that sweeps the globe or within your community, or that lies in the darker recesses of your own heart, waiting to terrorize you at any chance.

It is not a simple solution, because we have already nurtured evil to the point that it thrives and grows each day. At the beginning, Adam and Eve could have simply ignored it and it would have eventually dissolved into the sparks of G‑dly light they revealed in the Garden. But once Evil has been fed and lives out of its bag, it can never be dealt with so smoothly again.

Nevertheless, our major weapon against Evil is still our disregard for it. This is perhaps the Lubavitcher Rebbe's most common response to those who wrote asking for counsel to deal with the Evil in their daily lives — whether it be anger, temptation, disturbing thoughts, bad dreams, over and over, the Rebbe writes, "do more good and remove your mind from the issue." Even in matters of health, the Rebbe advised, "Find a good doctor, who will be concerned with your problems. Then simply follow his instructions and remove your mind from the sickness."

On a global scale, Evil is not something to fear, much less negotiate with. That only gives it more power. Yes, there are times when you have no choice but to battle Evil — as the Maccabees did against the Syrian-Greek oppressor. But stoop to conquer Evil and you will only join it in its mud. Against Evil, you must march to battle on the clouds. You must trample it while never looking down. On the contrary, while in battle against evil, you must find yourself reaching higher and higher.

That is why it is so important today for us to create more light. Even a little light pushes away a lot of darkness. For every shadow of darkness we have seen, we must produce megawatts of blinding light. Just as those possessed by evil did the wild and unreasonable, beyond that which the craziest doomsayer could have predicted, so, too, we must do kindness beyond reason.

In fact, this is the purpose of evil, why a G‑d who is entirely good devised evil to be in His world. Because evil forces us to reach deep inside, to find our inner strength, climbing ever higher, until reaching a brilliant, blinding light — a light that leaves no crevice for darkness to hide.

Against that light, Evil melts in surrender, having fulfilled its purpose of being. For, in the beginning, darkness was made with a single intent: To squeeze out the inner light of the human soul. A light that knows no bounds.

Fight evil with beauty. Defy darkness with infinite light.