it is necessary to distinguish following concepts:
intellectual, intellectual – a man engaged in mental work; in General it may be a fool, but to do well at intellectual tasks of some simple types;
intellectual genius – a man with an unbalanced psyche: pererasti with the ability to solve some class of intellectual tasks, developed at the expense of other mental abilities;
nerd – people with the increased capacity for intellectual action;
sage – wise man, pick up some practical knowledge, aware of his specific place in the world and adapt to it.