What is the primary basis for in personam jurisdiction over a person within New York?

The primary basis for in personam jurisdiction over an individual within New York is indeed presence within the state. This means that if a person is physically present in New York, the courts of New York can exercise jurisdiction over that person. The rationale behind this principle is rooted in the idea that individuals who are present within a state's borders are subject to the laws and authority of that state. This presence can be temporary or permanent; as long as the individual is physically in New York at the time of legal proceedings, the state’s courts can assert jurisdiction.

In contrast, registration as a business, while it establishes certain legal responsibilities and could affect jurisdiction in some cases, does not serve as the primary basis for in personam jurisdiction over individuals. Written consent to jurisdiction can create jurisdiction but typically requires explicit agreement, which is not as foundational as the principle of presence. Establishing residence in New York can also lead to in personam jurisdiction, but it is not the primary basis. The presence of an individual is the most direct and immediate ground for a court in New York to claim authority over a person.