'common sense'

"For in relation to reason on sense, in so far as it is the only thing that makes us human and distinguishes us from brute animals, I believe that it is present in each of us in its entirety, and thus I follow the view generally held by philosophers, who say that there are differences of degree only between 'accidents', but not between the 'forms' or natures of individuals in the same species" (Rene Descartes - Discourse on Method, Part One).

For me this means that common sense is a higher degree of an animals instinct, we all have animal instincts but we have learned to control them. Say that a deer hears a loud noise they react with immediate fear and will most likely run away to find cover. Now when we hear a loud noise, yes, we are startled but we don't run for cover, we think reasonable and think of what could have made that noise, our 'common sense' is telling us that it's not a threat.