A person lacking in common sense. (Merriam – Webster)
An ignorant, foolish, or silly person. (Dictionary.com)
If you call someone a simpleton, you think they are easily deceived or not very intelligent. (Collins Dictionary)
A person without the usual ability to use reason and understand. (Cambridge Dictionary)
A foolish or gullible person. (Oxford Dictionaries)
The top twenty five simpleton quotes.
The Book of Noodles: Stories of Simpletons; Or, Fools and Their Follies (Dodo Press)