Several years ago a campus publication ran a profile of me. Then a man I didn't know came over to me and called me an a------. His definition of an a------ was someone whose beliefs didn't "hang together." Either you were a liberal or a conservative, a Democrat or a Republican...or you were an a------.

Well, OK. Then I'm an a------.

I was fated to be an a------. I grew up in a secular Jewish household in an ethnically- and religiously-mixed working/lower middle class neighborhood in Philadelphia during the Cold War. My mother sat a vigil for the Rosenbergs; my oxymoronic father was a Jewish racist. I had uncles who were Taft Republicans, and Communist cousins. A neighbor was the Red who had headed the teachers' union; one of my history teachers was the guy who overthrew him.

My earliest TV memories are a mixture of Howdy Doody and the Army-McCarthy hearings, Groucho Marx and the Suez crisis. People sat around talking about Mohammed Mossadegh and J. Robert Oppenheimer. We got Saturday Review at home. I went to the library to read The New Leader (which I ended up writing for 25 years later) and The National Review. When I went off to college I subscribed to both.

I was a biologist, but found time to read Daniel DeLeon, I.F. Stone, Arthur Koestler, Emmanuel LeRoy Ladurie, Eugene Genovese, Robert Conquest.

Along the way I discovered that science was not the straightforward pursuit of truth one learned about in school. It, too, was full of interpretation, nuance, even ideology. It was the time of Thomas Kuhn and "scientific revolutions;" plenty of people were trying to be Lenin. I found that in science as in politics I was unable to embrace any totalizing ideology.

So now I'm nearing 60 and the more I see and the more I learn, the more afraid of ideology I become. About 30 years ago I discovered the political thought of Isaiah Berlin. The kernel of his philosophy is that ideology is the enemy of mankind. The fox knows many things, he said, but the hedgehog knows one great thing. I know it too: it's OK to be an a------.

Art Shapiro is a professor of evolution and ecology.