In a tort of intentional interference with contractual relations, what must the defendant do?

In the tort of intentional interference with contractual relations, the key element is that the defendant must act intentionally to induce a breach of an existing contract. This means that the defendant's actions must be deliberate, with the intention of causing a party to a contract to break that contract or to make it more difficult for them to perform their obligations.

The rationale behind this requirement is to hold individuals accountable for their actions that disrupt the contractual relationships of others, recognizing that intentional interference can lead to significant harm for the parties involved in the contract. It underscores the principle that individuals should respect existing contractual agreements and not actively seek to undermine them.

In terms of the other options, while it might be true that the defendant does not need to have knowledge of the contract for them to incur liability in other contexts, such absence of knowledge is not a requisite in this case, as the intent to interfere is crucial. The notion of liability when protecting a right does not inherently lead to an interference claim, and proving malice is not required to succeed in claiming intentional interference; rather, the focus is primarily on the intent to interfere with the contractual relationship itself.