Philosophy, which is Greek for "love of wisdom", is the quintessential spiritual pursuit. It requires you to think carefully about reality, using tools such as logic and argumentation to arrive at truth. Logic is the language that manipulates signs, and is the formal structure you parse your beliefs in. Mathematics is logical. A logical truth that is unavoidable is known as a tautology. An example of a tautology is “A=A”, which in English might be phrased as “whatever is, is”. On the other hand, a logical statement which is always false is a contradiction. In English, we might say “it is impossible for a thing to both be and not be” and the truth arises from the clear contradiction.
For every truth, there is an infinite number of falsehoods, and behind every known falsehood is a contradiction. A paradox is a belief that appears to be both false and true, a contradiction that cannot be false. Some beliefs are true. Others are false. True beliefs might be knowledge. The study of what makes a belief knowledge is known as “epistemology”, which is Greek for “theory of knowledge”.
You swim in a world of biases. Your own biases are difficult to see. If you attempt to tell the unvarnished truth, they will emerge: behind every attempt to tell the truth, bias follows like a shadow. Many biases come from the desire for the world to be one way. Scientists call this “confirmation bias”, which describes your tendency to want to be right. Being aware of such biases is the only way to remove them from your beliefs.
The systematic study of biases leads you to the world of fallacies. A fallacy is not necessarily false, but rather is an argument that does not necessarily follow from its premises. The "fallacy fallacy" arises when you ignore the truth of a statement because it is fallacious, not because it is false.
There are two main types of fallacies. The first are formal fallacies. These have to do with the structure of logic. An example is in order.
Stick with me, because this will come together at the end. A conditional statement is one where the antecedent is sufficient to prove the consequent. Say the antecedent is "p" and the consequent is "q". In this case, the conditional statement is "if p, then q". The antecedent "p" might represent the premise "it is raining", and the consequent "q" might signify "the ground is wet". So, the full conditional is "if it is raining, then the ground is wet". Clearly, if you affirm the antecedent (a process known as "modus ponens", or "the way that affirms by affirming", in Latin), then the consequent is true. Likewise, if you deny the consequent ("modus tollens", or "the way that denies by denying"), the antecedent is false. In other words, "if the ground is not wet, then it is not raining". You deny the antecedent by denying the consequent.
It is fallacy, but not necessarily false, that "affirming the consequent" means that the antecedent is true. "If the ground is wet, then it is raining" sounds true. However, there could be other reasons the ground is wet. A water main might have broken and soaked the roads. Similarly, "denying the antecedent" is a formal fallacy. "If it is not raining, then the ground is not wet" does not consider that there may be other reasons the ground might be wet. Notice that the conditional relies on observation to prove it. Although the form of a conditional is always the same, the individual facts require some insight into reality. The empirical world, the world of perception and sensation, cannot be removed from your investigation into reality.
Although there are a few more kinds of formal fallacies, such as the Fallacy of Four Terms (which deals with the formal structure of a syllogism), that is all I need to say about them for now.
The other kind of fallacy is informal, and does not depend on the four walls of logic. An argumentum ad hominem (“argument to the person”) denies the truth of an argument because of some irrelevant feature of the person making the statement. Another informal fallacy, the straw-man, builds an easily dismantled version of your opponent's argument and takes that apart, while leaving the actual argument intact. (The opposite of a straw-man is a “steel-man”, which builds up the most charitable version of your opponent's argument before trying to dismantle it.) An appeal to emotion, such as argumentum ad misericordiam (“argument from pity”), is a fallacy that tricks a person into accepting the truth of a premise by clouding their reason with emotional language. Some fallacies are parallel but opposite: appeal to tradition and appeal to novelty argue that one should agree with the conclusion because that is how it has always been, or, oppositely, because it is a new idea.
A non sequitur is an argument where the conclusion does not follow from the premises. Another fallacy is called “moving the goalposts”, which changes the win conditions that disprove your argument.
An equivocation, also fallacious, is when a word has more than one meaning, and you switch the meaning mid-way through the argument. For example: 1) nothing is better than ultimate happiness; 2) toast is better than nothing; therefore, 3) toast is better than ultimate happiness.
That last example was of a fallacious syllogism. A syllogism is a kind of deductive argument where two premises lead to a conclusion. A famous one is: 1) All men are mortal; 2) Socrates is a man; therefore, 3) Socrates is mortal. There are three terms in this syllogism: men, mortal, and Socrates. If there are four terms, the argument is invalid. In the toast example, the meaning of “nothing” is different in each use, thus there are four terms, therefore the deductive argument is formally fallacious.
Validity of an argument means that if the premises are true, then the conclusion is true. An invalid argument occurs when one or both premises are not true. A sound argument is one where the premises and conclusion are all true. When the conclusion is the same as one of the premises, you have a circular argument, also known as "begging the question". It is so common that there are many other ways to signify this fallacy. In Latin, it is “petitio principii” (“assuming the initial point”).
It is an uncomfortable fact that the truth of the logical method requires that a contradiction is always false. However, it takes a circular argument to establish the falsehood of all contradictions. Whether this is “viciously” circular, or a useful rule of thumb for developing higher level insights, is a matter of debate. Some philosophers discuss kinds of logic which allow for “true contradictions” (also known as “dialetheia”), but if we go back to Aristotle, the formalizer of logic, he simply said that it is of no use to argue with someone who does not believe that all contradictions are false.
The kind of logic I have talked about so far is known as "deductive logic". There is also inductive logic. An example of inductive logic is "all sheep I have seen are white, therefore all sheep are white". The problem with inductive logic is that it requires that the future always behaves like the past. One black sheep breaks the rule. Or you could wonder if only the sides of the sheep facing the observer are white. The Problem of Induction was described by the great skeptic, David Hume.
Another kind of logic is a blend of deduction and induction and it is called "hypothetico-deductive logic". In this format, you invent a hypothesis and deduce the consequences of this hypothesis. Then you test to see if the consequences occur in reality through controlled experiments. This is the primary method of science, and never produces the absolute certainty that you might find in a tautology or definition. This is not a weakness, but a feature. The scientific method, which is a little bit more than systematic common sense, is the best way to discover knowledge about reality.
The last kind of logic you might come across is "abductive reasoning". You might use this when troubleshooting a problem on your computer. You observe the state of your computer, and try to rule out hypotheses that do not explain the problem, until you narrow down on the actual problem.
This whole argument might seem a bit divorced from the happy mysticism of many spiritualists, but the point of philosophy is to capture reality, not to justify wishful thinking. There are many people who try to stress the importance of thinking outside of the box, but philosophy requires you first to learn how to think inside the box.
By recognizing that you, like everyone else, are prone to being tricked by cognitive distortions such as fallacies and biases, you can pick apart arguments. Since falsehoods vastly outnumber truths, being able to efficiently and accurately recognize falsehoods is important. The love of wisdom is the love of truth, and it is rare that your first thoughts are the final say in any matter, so you should always be prepared to change your mind. As Alvin Toffler said, “The illiterate of the 21st century will not be those who cannot read and write, but those who cannot learn, unlearn, and relearn.”
There are several kinds of reasoning that you might come across. Deduction, whether free-standing or accompanied by a hypothesis, is the least problematic.
These skills are developed best through practice. Healthy debate and discussion is the most common way to practice. The earliest philosophers, and many philosophers through the ages, built their theories on top of dialogues. The Socratic method, made famous by his pupil Plato, is a method that applies all that I have discussed here to try to work out the problems of philosophy. You ask questions and try to find contradictions in the answers. Socratic irony, a key feature of this method, has an inquisitor who feigns ignorance on the topic under discussion. If you are discussing the meaning of love, such as in Plato's “Symposium”, or the nature of justice in Plato's “Republic”, you ask questions that try to discover the truth from a position of uncertainty.
As Socrates said, “I only know that I know nothing”.