"Here (on one hand) is natural instinct and here (on the other) is control. You have to combine the two in harmony. If you have one to the extreme you'll be very unscientific. If you have another to the extreme you become all of a sudden a mechanical man."
Vertical thinking (left brain):
It's selective. It searches logic correction of ideas, choosing a path by excluding other possible ways and forks. It goes towards the best focusing to solve problems. It moves forward if there's a direction to move upon, if it seems to be a possible solution.
You have to walk to an objective, you know what you are searching. Vertical thinking is analytic, it's based on a sequency of ideas. You can only improve gradually, each step based --and firmly associated-- on the last, the validity of a conclusion being the correctness of each and all of the former steps.
Going to D means you've been on A, B and C before. Negation and judgment from vertical thinking block lateral deviations, which kills any possibility of finding the right answer from a wrong idea. Vertical thinking rejects all that seems not linked with the main theme; categories, classes and labels are permanent, all relying upon inflexible definitions such as Mathematical symbols.
Vertical thinking always follows the obvious road, the wider road, the best signposted road. And it's a finite process, hoping that in the end it will be a solution, and surely it will.
Lateral thinking (right brain):
Creative process in which matters the effectivity of conclusions achieved, always before settling any logical framework.
It follows all possible paths and finds new ones, searching new focusings and their potential. Lateral thinking advances to create new directions, being change and movement its tools of rearranging stablished patterns of concepts. Not necessarily moving to reach something, but to move away from it and consider it from a different point of view. Wants change by itself, as an experiment to start a switch of thoughts. You wander without direction, digressing around experiments, patterns, models, ideas. Movement is not a mean, but the way to orientate a reopening of the problem.
Lateral thinking searches before knowing what it has to search. It's provocative, not fearing to be wrong --leaping, skipping steps without having to follow any stablished order and filling in the blanks later. You can move from A to D by means of a parallel path, then moving retrospectively through C and then B. The validity of a solution doesn't depend on the correctness of the path you have walked, but by itself, and sometimes you can track the logic path back to the starting point; once established, it doesn't matter from which point you came from, although it was only possible from your ending point --something similar to climbing at the peak of the mountain to discover a better path you wouldn't have imagined otherwise. Lateral thinking hasn't to be correct step by step, as long as the final conclusion ends to be true.
Lateral thinking doesn't undervalue any possible way, having to walk past bad solutions to run across the right one; by keeping or rearranging the context, the idea turns up as true. Even explores what seems completely outside the point, associating external factors to force a decomposition of the models in his original components. Categories and labels are variable.
The focusing changes with the context, always following the least obvious way and deeply trusting in probability. Solution is never waranteed, but so does the chance of finding a better answer.
It's an almost perfect combination of both vertical and lateral performance of the brain in a single person --male, female, black, white, yellow or blue.
How many people of amazing thinking we have all over the world? Not clear enough, though its number seems to be inversely proportional to the population increase, and directly related to the deceasing of education, the killing of art/culture and the obliteration of individualism and personal goals --others than earning your money, expending your money.
I will always have happy memories of George W. Bush, Ariel Sharon, Tony Blair, José María Aznar, Silvio Berlusconi, Homer Simpson, et al.
All that's worthwhile in this text cames from Edward De Bono's book Lateral Thinking. A Textbook of Creativity.