The scientist who came up with the most widely accepted and used system for classifying living things was Carl Linnaeus. He is known as the father of taxonomy, the science of classifying organisms.

Linnaeus developed a hierarchical system of classification based on shared physical characteristics, which is still used today, though with modifications. This system includes seven main levels:

1. Domain: The broadest category (e.g., Bacteria, Archaea, Eukarya)

2. Kingdom: A large group of related organisms (e.g., Animalia, Plantae)

3. Phylum: A group of related classes (e.g., Chordata)

4. Class: A group of related orders (e.g., Mammalia)

5. Order: A group of related families (e.g., Primates)

6. Family: A group of related genera (e.g., Hominidae)

7. Genus: A group of closely related species (e.g., Homo)

8. Species: The most specific level, a group of organisms that can interbreed and produce fertile offspring (e.g., Homo sapiens)

While Linnaeus's system was groundbreaking, it has been updated and refined over time with the development of new technologies and discoveries, particularly in the fields of genetics and molecular biology.