Logical reasoning is a system of forming conclusions based on a set of premises or information. Commonly, logical reasoning is broken down into two major types called deductive and inductive reasoning. While the principles of logic can be used to create a strong argument for or against a conclusion, the system has several vulnerabilities, including the potential for untrue premises, fallacies, and intentional distortion of reason.
To reach a conclusion using logical reasoning, evidence or facts must first be presented. For instance, if a grocer wants to know if he is selling more beets than turnips, he may gather evidence about the amount of the two vegetables in recent shipments, how many have been sold, and if any product loss has occurred due to theft or damage. If his premises show that he sold 52 turnips and 75 beets in the same month, with no loss due to theft or damage, he can logically conclude that he sells more beets than turnips based on the evidence.
The type of reasoning in the above example is known as deductive reasoning. This type of logic occurs when the premises add up to a single, indisputable conclusion. Given that the premises are accurate, deductive reasoning can prove an absolute truth or fact. Inductive logic, by contrast, uses premises to determine a highly probable, but not absolute, conclusion. While inductive logical reasoning can be far more complex to understand than deductive reasoning, it generally forms the bulk of most logic-based arguments.
One type of inductive reasoning involves conclusions that have to do with the future. If the grocer from the first example wants to know whether he will sell more turnips or beets over the next month, an absolute answer becomes impossible to obtain, because chance enters the picture. Based on his past sales, the grocer might assume that since he sold more beets in January, he will sell more in February as well; however, if an E.coli outbreak in beets at the beginning of February makes people afraid to buy any, his initial conclusion may be false. Using his sales records and knowledge of buying trends, he may be able to formulate an inductive argument that suggests a high probability of selling more beets than turnips, but his premises cannot add up to an absolute guarantee.
Logical reasoning can be a good servant but a poor master. While the principles of using accurate premises to draw a strong conclusion may be admirable, they frequently break down when they are used incorrectly. A logical fallacy occurs when an incorrect or unsupported conclusion is drawn from premises. There are dozens of types of logical fallacies that serve as tripwires and pitfalls to good logical reasoning and must be avoided to ensure a sound, convincing argument.