Final answer:
Direction (X leads to Y but not vice versa) is an essential attribute of a cause.
Step-by-step explanation:
The statement 'Direction (X leads to Y but not vice versa) is an essential attribute of a cause' is true. In a cause and effect relationship, X is always necessary for Y but not vice versa. This asymmetrical relationship means that X leads to Y, but Y does not necessarily lead to X. For example, if smoking causes lung cancer, not all people with lung cancer necessarily smoke.