Think wrongly, if you please, but in all cases think for yourself.

Gotthold Lessing (1729-1781) German playwright, philosopher, dramaturg, writer

(Attributed)

I cannot find an original source, but as early as 1847 this phrase (or this English translation) was connected with him, and the quote is mentioned in his biography Gotthold Ephraim Lessing: His Life and His Works (1878), by Helen Zimmern, who translated a number of his pieces.

Frequently misattributed to the modern English author Doris Lessing, perhaps because it is so misattributed on Wikiquote. There it is cited to an interview by Amanda Craig, "Grand dame of letters who's not going quietly," The Times of London (2003-11-23). The reference there is behind a paywall, so it's unclear if Lessing actually says it in the interview, or it is erroneously referenced by the author.

The quotation is also attributed to the Egyptian philosopher Hypatia.