A subtle mathematical criticism regarding Alan Dershowitz's article "Surviving in a P.C. World" (April 28): The article opens with the following lines: "It has been widely reported that since 1988 more than half the marriages involving American Jews have been to non-Jews. If this data is accurate, more Jews now marry non-Jews than fellow Jews." It should be pointed out that the second statement does not necessarily follow from the first.

For example, let us assume 60 percent of marriages involving American Jews are to non-Jews. Then for every ten marriages involving a Jew, 6 will be between a Jew and a non-Jew, and 4 will be between two Jews. It is not hard to see that the 6 inter-marriages involve 6 Jews, while the 4 in-group marriages involve 8 Jews. Thus, in our scenario, in which a considerable majority of marriages involving American Jews are with non-Jews, 57 percent of Jews are still marrying within the religion.

Let it be noted that Dershowitz's data is not necessarily incorrect despite the flaw in logic outlined above. If a sufficient percentage (namely 67 percent) of marriages involving American Jews are inter-marriages, then it would, in fact, be true that a majority of Jews are marrying outside the faith. --Jeremy L. Lizt '97