Spiela verified

Deductive vs Inductive Reasoning: What’s the Difference?


We all claim to know certain things. You know that you love your partner. You know that coffee tastes bitter. And you know that climate change is really real. 


But how do we know those things? The above examples are illustrations of empirical deductions. Put simply, they are types of knowledge you come to through generalisations from observations. 


Suppose you see a tree for the first time and its leaves are green. Twenty years on, every tree you’ve ever witnessed in those 20 years has had green leaves. No one would bat an eyelid if you said “all trees have green leaves”, even if you haven’t seen every single tree in the world. That’s inductive reasoning. 


Things get a bit more complicated as some, if not most of our knowledge, is not based on personal observations. Instead, we rely on the testimony of others; testimony from our friends, teachers, scientists, professors and more. 


However, we can claim to know things with a different approach. Deductive reasoning is a more systematic method of finding the truth, or more accurately, reaching a certain conclusion. 


Suppose you found out that all humans are amphibians. Your lovely friend Sarah happens to be human. Therefore Sarah is an amphibian. This makes complete sense if you take “all humans are amphibians” to be true. Of course in the real world, we know that all humans are not in fact amphibians, but mammals. However, deductive reasoning helps map out what follows from what, so that you can be guaranteed you have the truth, so long as the premises are also true. 


As humans, we use both deductive and inductive reasoning to help us gain knowledge. Deductive reasoning only works if the premises are true. Yet the only way to know that is if we investigate the world around us. 


All this might seem obvious, so obvious in the fact that you execute these methods perfectly every day. It goes without saying though that we are prone to our own biases and sometimes neglect these reasoning skills. 


Sometimes we practice cognitive dissonance, the act of maintaining a belief in the face of contradictory evidence. We are not entirely rational beings, yet when it comes to our beliefs, we hold them to be True with a capital T. 


This is not to say we know nothing. The ultra sceptical view is not only paradoxical but unhelpful. Rather, we know things to a limited extent. We can push that extent if we practise deductive and inductive reasoning with most, if not all our  beliefs. Yes it’s mentally exhausting and time consuming. But, only then are we justified to know anything at all. 


Please login to drop a comment for this post. Click here