You can go across the world and come up more than a thousand different variations on the definition of rational and irrational. Whether any of those definitions are right are completely subjective to one's own opinion, right? People throughout the world come from different cultures and backgrounds. A person living in an Asian country might say its rational to eat dogs, while in a western country a person will most likely disagree and say it's absolutely irrational. There are so many opinionated takes on whether or not something is rational or irrational based on motive of culture and one's own personal behavior/beliefs. So how do we distinguish rational and irrational thinking excluding these values? Many influential people have come up with their own definitions of rationality and irrationality throughout history. A German sociologist named Max Weber came up with many theories of what is rational and irrational and broke the definition down into four separate defining categories. The first category he came up with is instrumental rationality. Instrumental rationality can shortly be described as "Practical reasoning that helps a person decide how to do things (efficiently perform technical tasks, resolve conflicts, solve problems, etc.) by regarding the factors involved in a situation as variables to be controlled". The second type of Rationality Weber came up with is belief/value orientated rationality. As the title is pretty self explanatory, Belief/value orientate rationality be described as reasoning based upon what one may believe in ethically, religiously, aesthetically, and etc. An example of someone who has very belief orientated rationality would be an extreme religious advocate. This person will may decisions based upon what his or her religion sets and would find them to be rational as he/she believes her religion to be rational. The third type of rationality Max come up with was affectual/emotional rationality. Emotional rationality is rationality based upon emotion. Many can argue that emotions and rationality completely oppose each other, but in some cases that is not necessarily true. Finally, the fourth category Max Weber came up with is ingrained habituation. Whether these categories are valid when looking at a dissected version of rationality is completely subjective. Max Weber's take on the definition of rationality makes things complex, while informative and well thought out, it seems that it could also be easily put into one sentence, rather than an entire paragraph. Many other definitions for rational thinking also arose from intellectuals throughout the years. A more recent definition comes from Bent Flybvjerg, professor, Research Director, Dr. Techn., Dr. Scient., and Ph.D. Dr. Flybvjerg describes how "The word "rational" derives from the Latin word "ratio," which means "reason" or "computation" and that "to be rational means having or exercising the ability to reason." Although to say being rational is having the ability to reason is seems slightly redundant, Dr. Flybvjerg goes slightly more in depth by stating "Rationality is closely linked to the concept of truth and both concepts are centrally placed in the constitutions and laws of liberal democracies". Summing up the definition of rational and irrational thinking into plain simple terms is the best way to satisfy everyone. Saying the definition of rational is to do something and be able to back it up with logical reasoning would make sense. As for irrational, it could be described as doing something and not being able to back it up with logical reasoning. But there is a slight dilemma with this definition. It's completely subjective to everyone that can back up their reasoning despite what the current behavioral norm may be. For example, if you ask a serial killer why he murders people, he might say that he does it because it makes him happy. Is it rational to do something that makes you happy?