http://www.knifeup.com/ Induction is when man integrates many small observation to make a large, grand observation. Deduction is when man uses a large, grand observation as a roadmap to find and explain other smaller observations. For me, induction is the most applicable and useful form of reasoning. There are many problems with living a life of deduction but the simplest explanation is a common experience: your roommate giving you a mean look. Lets say you walk home, open the door, and see your roommate sitting on the couch reading a textbook. He looks up for a second and, during that brief second, makes a mean face. If you were to use deduction, you must first be a psychology student because, unless you study psychology, you would not be aware of the theories about facial expressions. Physics, chemistry, and business students would have no theory to deduce from and would be loss. Now, you are a psychology student who know lots of theories about facial expressions and relationships. However, you now must decide which theory would be the best for this situation. The thing is, this situation is very specific and there is no theory directly applicable to it. Your choice as to which theory to apply is just as important as how you would apply the theory. If you did find a theory that somewhat applies to your roommate’s mean face, you must then think of a way to apply the theory to this situation. The application of a theory is hard since, unlike the theory world, there are constraints and limits in the real world. For example, you must think of a way to apply it before the situation becomes too old and your roommate has moved on. There are also 10,000 other variables that are occurring that might come into play and require their own theory as well. Maybe your roommate is on a bad diet and is missing out on B vitamins which makes him stressed out and that is why he gave you the dirty look? You wouldn’t know unless you were a nutritionist as well. In addition to that, not all parts of human life has been summarized into grand theories. Things like attraction, love, and relationships are the most basic human elements but there are no universal theory connecting them. What exists are several theories that only explain parts of human life and these theories do not exist in harmony. Economics explains how humans trade for goods but can not explain why people make bad purchases they later regret. Marketing explains why humans make bad purchases but does not explain how the economy as a whole works. Keynesian economics believe everyone is rational but marketers believe everyone is rational and irrational. These two schools contradict but but schools can still be right at the same time. Unlike deduction, induction is faster, lighter, and requires no education. If you see your roommate’s mean face, you would've realized that face was a mean face because humans are wired to read emotions (unless you have aspergers). From that, you can just come to the conclusion that something is upsetting your roommate--you know this because, at one point in time, you made that face as well and you just connected the two dots. A saying in NLP is that the map is not the territory. No idea can precisely map our human life and, because of that, if we were to based out actions only from grand ideas, our reactions would always be a little bit miscalibrated. Also, the grand theories all have boundaries and limits as to what is possible and impossible and, if we subscribe to this idea, we would limit our actions (and therefore potential) to stuff that is only within the theory. It is like a watermelon who is stuck inside a glass jar and, therefore, only grows to be as big as the jar. Living a life of induction allows us to be as great as we want to and this is one of the joys of being human. Living a life of deduction would result in people who are awkward, think too much, and not very responsive. Deduction works good for things that have perfect forms like math but very poorly for things that have abnormal psychology such as roommates.