Causality itself is an evolved conceptual tool that simplifies, schematizes, and focuses our representation of situations.
Nexus causality on the other hand is a different tool.
InWar and Peace, Tolstoy asks:
'When an apple ripens and falls, why does it fall? Because of its attraction to the earth, because its stem withers, because it is dried by the sun, because it grows heavier, because the wind shakes it….?'
Nexus causality is what Police and FBI will be using in the analysis of Boston marathon bombings:
“For how long the suspects have been planning the bombings? How did they build the bombs? From whom, where and how did they get logistic support? Etc.”
But the analysis will stop, when bigger questions are asked:
“Is there a link between this event and US foreign policy in the Middle East and why?”
“Should US administration continue to support religious fundamentalists in the Middle East, especially in Syria and why?”
As simply stated by Tooby:
“Our minds evolved to represent situations in a way that highlighted the element in the nexus that we could manipulate to bring about a favoured outcome.”