Being credulous refers to someone who is gullible, naive or overly trusting, believing things without question or proof. The antonyms for this word are skeptical, wary and cautious. Skeptical people are critical thinkers, who approach everything with a healthy degree of doubt and seek evidence and rational explanations before accepting things as true. Wary people are cautious and vigilant, especially when they come across something that seems too good to be true. They proceed with caution, expecting the worst and taking steps to protect themselves. Cautious people are also careful and prudent, which means they think before acting and do things with a careful consideration of potential risks and consequences.