preconception

noun

1. An opinion formed before obtaining adequate evidence, especially as the result of bias or prejudice.

   “With many of the more general preconceptions of socialist thought the connection of their more practical proposals is by no means at once obvious, and in consequence many men who believe themselves to be determined opponents of that system of thought become in fact effective spreaders of its ideas.”

   “He told RAIL: "We had no preconceptions, but you would assume a newer train to have better air quality than an older one. We found that was not necessarily the case.”

2. A prejudice that prevents rational consideration of an issue.

adj

1. (not-comparable)Preconceptional.