Ideas/ knowledge can only change in 3 ways:

• Preventing them from changing: you secure them from changing by justifying their truth, by adding arguments to them that say why they are true, e.g. appeal to authority arguments.
• Subjectively adding parts to them (without critically investigating) that you feel are missing / or throwing out parts that you feel are not needed
• Actually improving them: you find flaws in them and try to correct them