John Locke on Ideas

"Light being that which discovers to us visible objects, we give the name of 'obscure' to that which is not placed in a light sufficient to discover minutely to us the figure and colours which are observable in it, and which in a better light would be discernible." -John Locke, p. 289 Ch. XXIX

John Locke tells us that ideas can be separated into clear and obscure. Clear ideas are like simple ideas. When the mind sees a simple idea it is imprinted in the mind and can be easily reproduced to the mind later on exactly the way it was originally stored. Obscure ideas are just like complex ideas. Complex ideas are made up a number of small simple ideas. Sometimes these imprinted ideas are lost in the mind. This happens sometimes because the original idea was not significant enough for the mind to remember them or sometimes because the mind is too weak to be able to reproduce the memory.