I'm not sure when or where the phrase "think outside the box" originated. As I remember, my first exposure came with the introduction of the nine-dot puzzle. The idea was to draw no more than four lines without lifting your pencil that crossed through all nine dots. Most people stopped the lines on a dot, With that restriction, the problem is impossible to solve. But, if you extend the lines beyond the dots, the problem can be solved. Thus, in order to solve the problem you had to think outside the box. (By the way, there are many other creative solutions to the puzzle without thinking outside the box.)
I must admit that I used this example in the 1980s in training. However, I quickly realized that thinking outside the box wasn't the challenge. The real challenge, especially to business, is thinking creatively inside the box. That's where most of the real work gets done, and the most productive innovation.
There is something about the tension of a closed system and creativity. An artist painting a picture has the two-dimensional surface that is framed. Writers start with a blank slate and the limitations of the language. Sculptors start with a piece of stone or clay.
The Roman's use of the square in battle was innovative and almost impenetrable for many years. Fortresses are almost always rectangular. Forming a circle for defense, as in "Circle the wagons". What happened inside the circle or rectangle was essential to survival.
I wonder why the phrase was not "Think outside the circle". Circles have been around for a very long time. And, we're finding that a circle of people still has enormous power.
What I'm discovering is that it's not the network of people or the links between people that is key. I'm finding that it is the space between that's important. But, more about that later.
The seminar on Systematic Idea Generation by Mark Fox puts a different twist on things; what he calls thinking in another box. You can think outside the box, inside the box or in another box. Thinking in another box is a very appropriate metaphor for business. It will probably result in distinctive innovation, a source of great wealth.
I've attended Mark's seminar twice and found that I learned things both times. He has a unique way of looking at creativity with a fresh new set of techniques.