For Day 78, I discussed inductive reasoning — deductive reasoning is pretty much the opposite: it begins with a particular premise and moves to a conclusion.

For example, all birds are animals — swans are birds —  therefore all swans are animals. 

In essence, it’s the taking of a theory, where you then move towards a conclusion. This conclusion, however, can be falsified, tested and investigated to find out whether or not it holds up. 

Another example is — all swans are birds — white birds are swans — all swans are white. 

Clearly this could be tested, such as are all white birds swans and whether all swans are white.

And yet, even if is found to hold up — it doesn’t necessarily mean that it will hold up forever. Black swans are a great example of a discovery that led to ‘all swans are white’ being wrong. If a theory is right now, it doesn’t necessarily mean that it can’t be falsified in the future. 

Popular culture has brought the fame of Sherlock Holmes well beyond the original stories from the 1800s, and his method of solving uses both deductive and inductive methods. There’s a great blogpost on Danielle Kinkaid’s site that outlines how this is so, and I recommend it as one of the resources for this podcast.