This is because [[Theories are conjectured]] and [[People (and the explanations they make) are fallible]]. Explanations are error-prone. (Or problem-prone.) While [[Problems are soluble]] and [[Good explanations solve problems]], each problem solved reveals new and better ones. This suggests that knowledge growth is infinite so long as we retain the capacity to be creative and critical. See also: [[Knowledge grows through conjectures and criticism]].