This is a concept that I've always found interesting. This evening I recalled it and found a blog article with other classifications of order of ignorance. This is the version I already knew: 0OI: I have Zeroth Order Ignorance (0OI) when I know something and can demonstrate my lack of ignorance in some tangible form, such as by building a system that satisfies the user. 1OI: Lack of Knowledge. I have First Order Ignorance (1OI) when I don’t know something and I can readily identify that fact. 2OI: Lack of Awareness. I have Second Order Ignorance (2OI) when I don’t know that I don’t know something. That is to say, not only am I ignorant of something (I have 1OI), I am unaware of that fact. 3OI: Lack of Process. I have Third Order Ignorance (3OI) when I don’t know of a suitably efficient way to find out that I don’t know that I don’t know something. So I am unable to resolve my 2OI. In my words: Level 0 : I know the problem and I can solve it because I've already done it before. ...