COMMON SENSE v/s COMMON FACTORS -

 COMMON SENSE v/s COMMON FACTORS - 

We say that if you drop something, it will fall down. Now, this is not mainly because you dropped it. Of course if you didn't drop it, it wouldn't have fallen, mostly. But the stronger reason is gravity. The reasons gravity is the stronger reason are that 1. it is more importantly responsible for the phenomenon - the effect (the falling down) - i.e. than the dropping (since in space, dropping won't lead to falling down) and 2. also because it is present everywhere on earth. Let me elaborate on the second reason more. There are ‘common factors’ everywhere during one's life. Like gravity and people and buildings etc. They will be present in descriptions of most scenes and events, in general. So why repeat them again and again. Don't mention them. Assume them. That's how they become commonsense. Gravity is commonsense for most of us for all of our lifetimes. So the actual and relevant piece of commonsense or “common factor” here (i.e. when we talking of objects falling if dropped down) is, instead, that ‘gravity, which pulls things down is everywhere’. This is the common, repeating, assumed part, everywhere and everytime, during one’s life (since it is rarely that someone is going to go to a non-gravity zone in life). For someone who makes frequent trips to space and spends a significant portion of his life there, it wouldn't be so much of a “common” sense that ‘if you drop things they will fall down’. 

Similarly we say that - "it is commonsense that if you cut a finger, it will start bleeding. But if it is the finger of a statue, it won't". Here the relevant actual piece of commonsense is that ‘most fingers are human fingers’. This is the common “FACTOR” ruling everywhere and everytime, which is responsible for the piece of commonsense of ‘bleeding if you cut a finger’ existing. This is also responsible for that piece of commonsense being uttered and mentioned the way it is. Note : you didn't mention gravity while saying the piece of commonsense that 'if you drop something it will fall down'!