What is the Difference Between Logic and Reason?

Understanding Logic and Reason

Reason and logic are two closely related forms of thinking involving the comparison of concepts. Both can be studied in terms of mathematics or philosophy and can be considered together as well as apart.^[1][2]

Before we get started, consider the following example, as speaks to the foundation of logic and reason (and thus also illustrates the key differences between the two):

• Concepts/terms are the comparison of attributes (Conception). Ex. 1, 2, 3, =; or, blue ball, red chair.
• Judgements/propositions are the comparison of concepts/terms (Logic). Ex. 1+2=3; or, x+2=3; or, the blue ball is on the red chair.
• Inferences are the comparison of judgements/propositions (Reason). Ex. Since 1+2=3, and since x+2=3, therefore we can infer x=1; Or, since the blue ball is on the red chair, and the blue ball can only be in one place at a time, therefore I can reason that the blue ball is necessarily not on the ground.

Meanwhile, each step above, from conception, to forming logical judgements as propositions, to then drawing reasoned inferences, follows a logical rule-set and requires increasingly complex degrees of reasoning.

This is one way to illustrate the core of how logic and reason differ and relate. Below we explain the details.

TIP: The example above is hierarchical. Reason deals with both logic and concepts, logic deals with concepts, and concepts are essentially just terms. Thus, while logic and reason are different, they are also closely related in that almost all types of reasoning utilize logic (and both logic and reasoning involve comparing concepts). With that noted, a term can exist without logic or reason, for example “blue ball,” logic can exist without reason but generally must use concepts, for example “1+2=3,” and in most cases reasoning will always involve using both logic and concepts, for example “since the blue ball is on the chair, then it is necessarily not on the ground.”

The Basics of Logic and Reason

In simple terms, logic describes comparing concepts/terms like 1, 2, or 3, using formal rule-sets like x+y=z, and reason describes drawing inferences from the comparison of logical rule-sets and terms, like since 1+2=3, and since x+2=3, therefore x is probably 1.

With that said, both logic and reason speak to very specific parts of the human process of thought. From our conception of rational and empirical data, to the related art/science of working with our thoughts about these things in the language form, we can call this whole… concept… logic and reason, just “reason,” very loosely just “logic,” or logical reasoning (which by any name is the art/science of comparing terms using logic and reason).

Consider the different ways we can use these terms, all of which are fully correct:

• One can either use the terms logic and reason as synonyms to describe the method of logical reasoning as a whole (where deductive logic and deductive reasoning essentially mean the same exact thing for example),
• One can use the terms in context where logic describes specific rule-sets that produce definite outcomes and reason describes the art of drawing inferences.
• One can describe logic and reason as two steps within logical reasoning where the first step is conceptualizing a term, for example, “look, there is an A and a B (each defined by their attributes).” Then logic describes judgements that compare concepts/terms, for example, “A=B and B=C.” Then reason describes conclusions inferred from that logic such as “since A=B and B=C, therefore A=C.”
• One can say logic describes that sort of “If…then…” logic that computers and calculators use, and reason describes the sort of critical thinking humans use to create computer programs and to make clever use of their outputs.
• In fact, one can say a lot of different things, each time using terms like “inference,” “deduction,” “concept”, “logic”, and “reason” in maddeningly different ways… but let’s not go down that rabbit hole yet.

So then, in general, logic describes rule-sets and reason describes inferences, but that aside, both are part of logic and reason and thus, the difference depends partly on context and is a bit semantical and interchangeable (especially when we use the terms in modern language).

To better illustrate the difference between logic and reason it will help to understand the three basic parts of thought which we eluded to above. Or let me rephrase that, with the introduction covered, the next section explains the most useful and correct way to understand Logic and Reason as a mode of thinking, as a science/art, and as a formal study.

Terms, Logic, Reason, and Skepticism

With that covered, let’s return to our three-aspects of thought example we started the page with (as that really is the key here).

Speaking loosely, there are three basic parts of thought (which bring us from conception/concept, to judgement/proposition, to drawing inferences) and therefore there are three natural parts of logical reasoning. They work like this:

1. There are terms or concepts we conceptualize by rationalizing or observing (by comparing attributes); like Socrates, men, or mortality.
2. There are logical judgements (propositions) we get by comparing terms; like Socrates is a man, and all men are mortal. <— This is Logic
3. Then there are reasoned inferences we get by comparing judgements and propositions; like since Socrates is a man and since all men are mortal, therefore Socrates is mortal. <—This is Reason

Then, one could reason further and apply skepticism by asking, “how do we know all men are mortal?”

In fact, there are many different types of reasoning, just like there are many ways to compare terms in logical propositions (AKA statements)… and thus we can do much more than just contradict and be skeptical like Socrates.

For example, we could reason further by creating the grounds for a hypothesis by pondering, “since energy can’t be created or destroyed, perhaps men aren’t truly mortal? After-all, all men are made of energy…. maybe this is a virtual simulation?”

Meanwhile, one can apply logical rule-sets to that skepticism and hypothesis, just like the scientific method does. Ok, now we have a hypothesis, its time to look for empirical data and apply formal rule-sets so we can get published!

Perhaps we want to collect facts to prove/disprove our hypothesis, the art of knowing which facts to collect is a thing of reason… but the structure of those facts will follow some rules of formal logic. We will make reasoned arguments with those facts, but the structure of our arguments and our propositions will be logical.

From all this we can… infer… that logic is a judgement (statement) with an expected outcome, like a rule-set (A+B=C), and reason is the act of critical thinking, combining, associating, questioning, and drawing inferences from judgements.

Meanwhile terms (themselves a collection of attributes) are what is being worked with in logic (and thus in reason as well), and skepticism is one example of the art of questioning inferences and propositions.

Together, these parts of logic and reason, which can be denoted as term, proposition, and inference, are three increasingly more complex and often probabilistic modes of thought (modes of conceptualizing and comparing terms, judgements, and inferences).

Are logic and reason arts or sciences? The answer is they are both. There is both an art (an action refined by practice) and a science (a type of knowledge refined by study) to reason and logic. Or, there is a certain art to reasoning with the science of logic. Or is there?!

TIP: Logical reasoning can be divided into three main types: deduction, induction, and abduction (three methods of logical reasoning), meanwhile arts like rhetoric and acts like being critical and skeptical and thinking “outside of the box” are aspects of using our reason.

TIP: As you may have gathered, it is near impossible to reason without logic (as logic precedes reasoning).

Terms, Logic, and Reason With a Syllogism

The simplest example of using both logic and reason is the Syllogism already eluded to above.

One could describe the syllogism as a thing of logic (its barebones are really just a logical rule-set), but lets discuss it as a thing of logic and reason (where our conclusion is our inference and we see the syllogism as a logical rule-set for making reasoned judgements).

A syllogism is a logical argument that applies Deductive Reasoning (AKA Deductive Logic), to arrive at a logically certain conclusion based on the comparison of two or more propositions (statements, premises, judgements; two or more logical conclusions based on conceptions).

Consider the classic example of a deductive argument (a logical argument):

1. All men are mortal. (judgement; we reasonably assume all men are mortal).
2. Socrates is a man. (judgement; we look and see he is a man).
3. Therefore, Socrates is mortal. (inference; we draw the logical conclusion Socrates is mortal).

There is logic to the above line of reasoning (since all men are mortal, and since Socrates is a man, Socrates is mortal), it is a consistent rule-set (so it is logic in that sense), but it is reasoning because one is deducing inferences to draw conclusions from judgments.

Reason as a Synonym for Applying Logic

In the above section on the syllogism all we really did was work with logic, but the term “reasoning” was used a lot (even though we didn’t do any complex reasoning like compare syllogisms or approach our conclusions in a skeptical manner).

This is, as noted in the introduction, generally explained by the fact that we use our language loosely (and often use logic and reason as synonyms).

Synonyms and Syllogisms aside (sorry), logic and reason are two very different parts of the same puzzle (AKA the process of thought). So let’s look closer at how they are different by expanding on the concepts we have already introduced.

TIP: As you may have already noticed, most of the time terms, judgments, and inferences are bumping up against each other (making them hard to discuss alone). Reasoning always involves terms and logic, logic always involves terms but can involve little to no reasoning, and terms only require the most basic forms of logic and reason to conceptualize. Pure logic (only logic) like mathematics requires almost no reasoning, a computer can do pure logic based on terms and make judgements. Meanwhile, advanced AI aside, comparing judgements and employing reason is a very human thing.

A Definition of Logic and Reason

At this point we can define our terms again as:

• A Term is a name for any concept we have conceptualized. Conception (process of thought) -> Concept (product of thought) -> Term (name we use in language).
• Logic tends to seek absolute truth via a series of judgements using specific rule-sets (like 1+1 = the judgement of 2, or Socrates + the features of a man = the judgement Socrates is a man). Judgement (the process form) -> Judgement (the product form) -> Proposition (language form).,
• Reason compares judgements and draws inferences associating terms and logic to seek probable truths and deeper understanding via a mix of formal and informal rule-sets (a sort of critical thinking that uses logic, skepticism, justified beliefs, philosophy, hypotheses, and many other modes of thought to draw inferences from judgements, terms, and reasoned arguments; reasoning is the process of deduction, induction, and abduction). Confusingly, an inference is always called an inference in any form (there is that pesky english language being confusing again!)

How Logic and Reason are Different – Consider Terms, Judgements, and Inferences

To view this another way, let’s look at an excerpt from a very simple and insightful resource on logic, the mostly forgotten (but free online), Deductive Logic by St. George William Joseph Stock):

There are three processes of thought that all relate to each other. The reason we want to phrase these three different ways is because there are at least three parts to thought.

§32. There are three processes of thought (what is happening when we think):

1. Conception
2. Judgement
3. Inference

§ 36. Corresponding to these three processes there are three products of thought (once we have thought we get):

1. The Concept.
2. The Judgement.
3. The Inference.

§ 38. When the three products of thought are expressed in language (when we express our thoughts, they are):

1. The Term.
2. The Proposition.
3. The Inference.

In other words:

There are three categories of logic:

1. Conception -> Concept -> Term. This category can be expressed as Terms / Concepts.
2. Judgement (the process form) -> Judgement (the product form) -> Proposition (language form). This category is Logic / Propositions.
3. Inference (the process form)  -> Inference (the product form) -> Inference (the language form). This category is Reason / Conclusions / Inferences.

TIP: So really there are three basic things to deal with here that share names and get many names, but have specific meanings depending on context. So simple concept, but kind of tricky to master. Don’t worry about mastering it, just get the three basics: terms, logic (propositions), and reason (inferences). Those are the key elements of a deductive argument (plus, as we’ll discuss in a second and eluded to above, “the relation”).

Then this relates to the idea that:

1. The concept is the result of comparing attributes.
2. The judgement is the result of comparing concepts.
3. The inference is the result of comparing judgements.

And likewise (to phrase the same thing in different words):

1. The term is the result of comparing attributes.
2. The proposition is the result of comparing terms.
3. The inference is the result of comparing propositions.

The Laws of Thought

Compare all of that to the idea that the laws of thought are all reducible to the three following axioms, which are known as The Three Fundamental Laws of Thought:

1. The Law of Identity: Whatever is, is; or, in a more precise form, Every A is A.
2. The Law of Contradiction: Nothing can both be and not be; Nothing can be A and not A.
3. The Law of Excluded Middle:  Everything must either be or not be; Everything is either A or not A.

TIP: And here I would also note, especially if we were discussing induction, that we must also consider the “laws of probability” (a thing can be in a state of superposition or can be “likely A” or “likely B.”)

And we have all the tools we need to use to understand and employ logic and reason.

The rule-sets and the judgements made from comparing terms are logic, and the inferences made from comparing propositions is reason, meanwhile terms are the names given to concepts.

Or, in simple logic:

1. Observe concepts. ex. men, mortals, Socrates, Plato.
2. Make judgements about concepts (logic). ex. All men are Mortal, Socrates is mortal, Plato is mortal.
3. Compare judgements and make inferences (reason). ex. If Socrates and Plato fight to the death, there can be only one left alive, after-all, all men are mortal, even the great Socrates.

TIP: In other words, reason deals with probabilities and logic deals with absolutes (and therefore deduction is most logic and induction and abduction more things of reason). Logic seeks A + B = C judgements, and reason works with those judgements. Both are aspects of the art and science of comparing terms (where a term is A or B itself).

TIP: these modes of thought are all different, they have the same general end, which is the approaching of truth and understanding.

Examples of Logic and Reason

Logic is what makes a computer’s brain work, and reason is the skill one uses to fact-check using a search engine (comparing articles, being skeptical, applying logic, spotting false information based on experience, etc).

Logic is solving mathematic equations, reason is thinking of new ways to apply, combine, and refine those equations and the art of drawing inferences from them (the art of using deductive logic).

Moving On and Other Definitions

With the above said, given the close relation of logic and reason, and the sea of definitions from 300’s BC to today, I’m not going to offer a single specific answer as to exactly how to define logic and reason.

Rather, as I’ve already done above, I’m going to continue to offer many examples of the ways in which logic and reason relate and differ, offering my own opinions, and resources like Wikipedia definitions and insight into classical texts on logic.

So then, before we move on, here are the Wikipedia definitions:

• Logic is generally held to consist of the systematic study of the form of arguments. A valid argument is one where there is a specific relation of logical support between the assumptions of the argument and its conclusion. (In ordinary discourse, the conclusion of such an argument may be signified by words like therefore, hence, ergo and so on.)
• Reason is the capacity for consciously making sense of things, applying logic, establishing and verifying facts, and changing or justifying practices, institutions, and beliefs based on new or existing information. It is closely associated with such characteristically human activities as philosophy, science, language, mathematics, and art and is normally considered to be a definitive characteristic of human nature. Reason, or an aspect of it, is sometimes referred to as rationality.

TIP: In words, Reason is what makes us human, logic is what we often use to reason, both are modes of human thinking, but (cognitive AI aside) only logic can be mimicked by a modern machine. I keep using the computer analogy here, sorry.

Logic vs. Reason

With the above definitions in mind, the first thing to know about logic and reason is… that I’ve never seen the terms logic and reason defined perfectly (I’ve seen them defined very well many times, but never “perfectly”).

With that said, certainly, logic is the A+B=C science one (it is a formal system with clear rule-sets), and reason is the more broad and loose “art of critical thinking” that uses logic as one of its tools (it is a more informal system of induction, deduction, and associating that mixes in beliefs, opinions, and facts and rationalizes toward many ends).

Orators and philosophers use reason liberally, while the insurance adjuster generally sticks to logic.

Still, outside of very specific cases, it is hard to do any sort of thinking that doesn’t employ concepts, logic, and reason.

There are correct ways to reason (valid vs. invalid, sound and unsound), but the system has somewhat loose bounds beyond this… meanwhile logic demands rules so exact that a calculator could follow them flawlessly.^[3]

Logic is more a thing of the empirical, reason more theoretical. Logic is more a natural science, reason well suited for moral philosophy. A skeptic uses reason to deduce a range of probable answers, logic is binary.

Reason uses logic, but logic doesn’t have much need for reason after the rule-set has been formulated.

Reason is more like the human brain, pulling from experience, logic, ethics, morals, and tastes, considering many complex layers, associating and combing ideas, and logic is more like the cold and hard mathematics of a calculator.

With that in mind, Reason is more a thing of philosophy and critical thinking that moves one toward understanding of any sort, it can follow logical rule-sets, but can also use beliefs and opinions, it seeks truth and understanding over consistent answers (and can even be used to sway opinions, such as in oration and rhetoric).

A debater reasons, a lawyer reasons, and a person reasons with their friend to get them to share their cake.

Those who reason almost always use an assortment of different types of logic in their reasoning.

Logic is more a science that involves a series of judgments that includes formal logic like that used in mathematics and computing, and deductive logic (where conclusions are drawn from premisses).

A computer uses logic, a statistician uses logic, and a person reasoning often uses logic in their reasoning.

So, one would use logic to program a computer, but one might use reason to come up with easier ways to program the computer.

It makes sense to use logic in your reasoning, but logic itself doesn’t always require the use of reason.

In this sense we can say reason is a broad category of thinking, where logic is the aspect of thinking that can be translated to actionable and consistent rule-sets.

To frame this another way:

Logic is a science that uses defined rule-sets that produce consistent answers, reason is an art that describes all forms of critical thinking which seek understanding.^[4][5][6][7]

Both seek understanding, but logic is what makes a computer run, while reason is what made Jobs and Woz decide to build computers.

One doesn’t use reason to do their math homework, they reason with their mother to stay home from school.

One might use logic in a debate, but the art of rhetoric can sometimes involve using reason and not logic.

• Thus, Reason generally uses logic, although it doesn’t have to (one can use specific rule-sets in their reasoning such as because A is true, therefore B is also true; but they can also say, “knowing B is true, how can I use this to convince a person of C”).
• Meanwhile, logic doesn’t generally require reasoning (as finding “X” in the equation 1+X=2 requires nothing more than a rule-set).

ON LOGIC: A master of logic was Lewis Carrol (the guy who wrote Alice in Wonderland). Alice is actually a story poking fun at theoretical mathematics and almost all of his works are about logic. If you like your brain, you’ll love having it destroyed by Lewis’ “so far from Alice it stops being funny pretty quickly, and then becomes fun again” Symbolic Logic. The more logic you know, the better you’ll be able to reason, so if Carrol’s name isn’t reason enough… I mean, logically speaking. Ok, maybe that didn’t sell you, but if that is overwhelming try a System of Logic, Ratiocinative and Inductive by John Stuart Mill (it is even more burly and will make you appreciate Carrol). Sorry, bad joke. Do read those, but start with Carrol’s Game of Logic (there is cake!) If you understand logic, you understand reason, reason is logic and then everything left over pertaining to critical thinking.

How to Argue – Philosophical Reasoning: Crash Course Philosophy #2

Reason can be used to seek any truth or understanding, but its inputs aren’t limited to facts and rule-sets. One can reason using emotions, opinions, or beliefs, and can arrive at illogical answers.

Reason is a process of critical thinking, but the result doesn’t define it.

For example, I can say, “I believe in Santa, and I want Santa to get me a unicorn, and I have only enough ingredients to make chocolate chip or blueberry cookies, since I don’t think Santa’s reindeer like chocolate, I’ll make the blueberry cookies.”

That line of reasoning is actually valid, even though nothing in the story is fact-based.

We can say the line of reasoning was “logical,” as it followed a rule-set… but I certainly would describe it as “logic-of-the-highest-order”.

Meanwhile, if I say, “I believe in Santa, and I want Santa to get me a unicorn, so I’m going to go steal stuff…” that reasoning is not very good. Santa doesn’t get bad kids presents, so stealing stuff is not (logically speaking) going to net one a Unicorn. In other words, my logic was off in my reasoning, so my reasoning was not good.

Logic and reason are both things of “pure reason”, but where logic deals with formal rule-sets most often applied to the natural sciences, reason can pull from anything and be applied to anything.

So, while the distinctions are somewhat semantic in every day language, there is a world of difference between the formal science of logic (which can make a computer run), and the more ethereal art of reasoning (which is what Google tries to get its search engines to do with endless lines of coded logic when you ask it “what is the difference between reason and logic”).

All the Enlightenment founders used reason, but Newton’s mathematics are a thing of logic. We can apply reason, even when we don’t know all the facts logically.

To end, I’d say this:

• Logic is the science of following a rule-set that produces consistent results.
• Reason is the application of “pure logic,” empirical evidence, experiment, and skepticism to find truths, facts, and theories (AKA “critical thinking”).
• Enlightenment is simply the natural conclusions to which reason leads.

In other words, if the goal is enlightenment, the foundation must start with logic, and to do logic, we must properly define our terms.

TIP: Logic and reason are also music programs. Great ones actually. In music, learning the intervals and chords and scales is a thing of logic, but improvising with those rule-sets is a thing of reason. 😀

Logic –The Structure of Reason (Great Ideas of Philosophy)

1. Reason
2. Logic
3. Validity and Invalidity, Soundness and Unsoundness
4. What is the difference between logic and reason?
5. What is Kant’s argument about the relationship between logic and reason?
6. Logic
7. Classical Logic