premise: Walter Joseph De Maria (October 1, 1935 – July 25, 2013) was an American artist, sculptor, illustrator and composer, who lived and worked in New York City. Walter de Maria's artistic practice is connected with Minimal art, Conceptual art, and Land art of the 1960s.
hypothesis: Walter Joseph De Maria died when he was less than 77 years old.
reason: Based on the birth and death dates given in the context statement, Mr. De Maria died when he was 77 years, so he could not have died when he was less than 77 years old.