In search of that very “Idea”!

What is that I am searching? It's the most general/regular problem that I am searching to give it a shape of an idea. Then what is it that I am searching? I make round and round but fail to find its origin. It looks like a grayish shadow with a mask around; since long time…still I am unable to go near it! What is it after all I stumble most often and everyone else do face it with equal horror?