This week I took part in a conference on anti-Semitism in Europe. Hosted by the president of the European Commission Romano Prodi, the conference brought together leaders from around the world determined to fight the new wave of anti-Semitism that has engulfed Europe over the last few years.

The question is how the sincere intentions of the participants to combat this evil can be translated into effective action.

My experience has convinced me that moral clarity is critical in taking a stand against evil. Evil cannot be defeated if it cannot be recognized, and the only way to recognize evil is to draw clear moral lines. Evil thrives when those lines are blurred, when right and wrong is a matter of opinion rather than objective truth.

That is what makes the battle against the so-called new anti-Semitism so difficult. To the free world's modern eyes, classical anti-Semitism is easily discernible. If we watch films that show Jews draining the blood of Gentile children or plotting to take over the world, most of us would immediately recognize it as anti-Semitism.

Such movies, produced recently by the government-controlled media in Egypt and Syria and broadcast via satellite to hundreds of millions of Muslims around the world, including millions of Muslim immigrants in Western Europe, employ motifs and canards that are familiar to us.

But the new anti-Semitism is far more subtle. Whereas classical anti-Semitism was seen as being aimed at the Jewish religion or the Jewish people, the new anti-Semitism is ostensibly directed against the Jewish state. Since this anti-Semitism can hide behind the veneer of legitimate criticism of Israel, it is much more difficult to expose.

In fact, over the past year, whenever we have criticized particularly virulent anti-Israel statements as being rooted in anti-Semitism, the response has invariably been that we are trying to stifle legitimate criticism of Israel by deliberately labeling it anti-Semitism.

What emerged from this conference was an admission by European leaders themselves that not all criticism of Israel is legitimate. This recognition was evident in the remarks of President Romano Prodi, German Foreign Minister Joschka Fischer and other officials.

If not all criticism is valid, how then do we define the boundary line?

I propose the following test for differentiating legitimate criticism of Israel from anti-Semitism. The 3D test, as I call it, is not a new one. It merely applies to the new anti-Semitism the same criteria that for centuries identified the different dimensions of classical anti-Semitism.

The first D is the test of demonization.

Whether it came in the theological form of a collective accusation of deicide or in the literary depiction of Shakespeare's Shylock, Jews were demonized for centuries as the embodiment of evil. Therefore, today we must be wary of whether the Jewish state is being demonized by having its actions blown out of all sensible proportion.

For example, the comparisons of Israelis to Nazis and of the Palestinian refugee camps to Auschwitz – comparisons heard practically every day within the "enlightened" quarters of Europe – can only be considered anti-Semitic.

Those who draw such analogies either do not know anything about Nazi Germany or, more plausibly, are deliberately trying to paint modern-day Israel as the embodiment of evil.

The second D is the test of double standards. For thousands of years a clear sign of anti-Semitism was treating Jews differently than other peoples, from the discriminatory laws many nations enacted against them to the tendency to judge their behavior by a different yardstick.

Similarly, today we must ask whether criticism of Israel is being applied selectively. In other words, do similar policies by other governments engender the same criticism, or is there a double standard at work?

It is anti-Semitism, for instance, when Israel is singled out by the United Nations for human rights abuses while tried and true abusers like China, Iran, Cuba, and Syria are ignored.

Likewise, it is anti-Semitism when Israel's Magen David Adom, alone among the world's ambulance services, is denied admission to the International Red Cross.

The third D is the test of deligitimation. In the past, anti-Semites tried to deny the legitimacy of the Jewish religion, the Jewish people, or both. Today, they are trying to deny the legitimacy of the Jewish state, presenting it, among other things, as the last vestige of colonialism.

While criticism of an Israeli policy may not be anti-Semitic, the denial of Israel's right to exist is always anti-Semitic. If other peoples have a right to live securely in their homelands, then the Jewish people have a right to live securely in their homeland.

To remember the 3D test I suggest we recall those 3D movies we enjoyed as children. Without those special glasses the movie was flat and blurred. But when we put on our glasses the screen came alive, and we saw everything with perfect clarity.

In the same way, if we do not wear the right glasses, the line between legitimate criticism of Israel and anti-Semitism will be blurred and we will not be able to recognize this ancient evil, much less fight it.

But if we wear the special glasses provided by the 3D test – if we check whether Israel is being demonized or deligitimized, or whether a double standard is being applied to it – we will always be able to see anti-Semitism clearly.

And with moral clarity, I have no doubt that our efforts to combat this evil will prove far more effective.

The writer is Israel's Minister of Diaspora Affairs and Jerusalem