Determing causality is difficult, in part because the word causality has multiple meanings.

1. Prediction (aka Sufficiency). X causes Y to happen in the sense that if I do X Y happens more than I would expect by chance.
2. Explanation (aka Necessity). X causes Y to happen in the sense that Y cannot happen without X. This suggests that X is integral to Y’s realization.

In graduate school, I remember being taught that one can say that one thing causes another only if both things are true. Requiring (1) and (2) to both be true is equivalent to enforcing a biconditional.

\begin{aligned} X &\rightarrow Y\\ \neg X &\rightarrow \neg Y \quad \textrm{by contrapositive } Y \rightarrow X & \therefore X \leftrightarrow Y \end{aligned}

The notation brings out a limitation of this reasoning. It is first-order logic and brooks no conditionality.