I contend we are both atheists. I just believe in one fewer god than you do. When you understand why you dismiss all the other possible gods, you will understand why I dismiss yours.

Stephen F. Roberts (b. c. 1969) American software developer

Usenet, alt.atheism, sig line (early 1995)
    (Source)

See Roberts' "Brief History of the Quote" for more on its origins.

As he is not a prominent public figure, the quote is frequently attributed to others, usually of the same name. Possibly most famously, Sam Harris misattributed it to Australian historian Stephen Henry Roberts in his article "10 Myths -- and 10 Truths -- about Atheism," Los Angeles Times (2006-12-24) (since corrected by Harris).

The quotation is often given with an extra word: "I contend that we are both atheists ...." Roberts himself uses the shorter version.