sceptical
scep-ti-cal
adjective
Having doubts or reservations about the truth or existence of something.
"She remained sceptical about his claims."
adjective
Unwilling to believe something without proof; questioning accepted beliefs or facts.
"Scientists are often sceptical of new theories."
Thesaurus
Synonyms: skeptical, distrustful, questioning, doubting, unbelieving, disbelieving, incredulous