Which of the following is NOT considered a fault-based ground for divorce?

Irreconcilable differences stand out as the correct choice because it is not categorized as a fault-based ground for divorce. In many jurisdictions, including New York, irreconcilable differences fall under no-fault grounds for divorce. This means that a spouse does not need to prove wrongdoing by the other party to obtain a divorce. Instead, it simply indicates that the marriage has broken down irreparably due to significant disagreements and conflicts.

In contrast, desertion, insanity, and adultery are considered fault-based grounds for divorce. These grounds require one spouse to prove that the other has engaged in specific wrongful conduct leading to the breakdown of the marital relationship. Desertion involves one spouse abandoning the other without justification, insanity typically refers to a mental illness that has rendered a spouse incapable of fulfilling marital obligations, and adultery involves one spouse engaging in sexual relations with someone outside the marriage. Each of these fault-based grounds necessitates a demonstration of the other party's misconduct to justify the divorce.