Passage: A conservationist may be inspired by the resource conservation ethic, which seeks to identify what measures will deliver "the greatest good for the greatest number of people for the longest time." In contrast, some conservation biologists argue that nature has an intrinsic value that is independent of anthropocentric usefulness or utilitarianism. Intrinsic value advocates that a gene, or species, be valued because they have a utility for the ecosystems they sustain. Aldo Leopold was a classical thinker and writer on such conservation ethics whose philosophy, ethics and writings are still valued and revisited by modern conservation biologists.

Question: what type of thinker was aldo leopold considered?
a classical thinker