That is true, Gödel's incompleteness theorem dates to 1931. In 1944 Gödel published his first philosophical paper, entitled "On Russell's Mathematical Logic".

That is true, Gödel's incompleteness theorem dates to 1931. In 1944 Gödel published his first philosophical paper, entitled "On Russell's Mathematical Logic". The mistake was probably made because the author Julian Baggini is a philosopher and so he is mostly aware of Gödel's philosophical works and not so much of his mathematical accomplishments.