Taken as a whole, Holmes Ralston III’s Eco-ethics unfolds its theoretical approach from the perspective of ontology of natural value. As a result, it exceedingly inherits Leopold’s earth ethics in view of objectivity. Ralston emphasizes that we should not neglect that the existence of natural value depends on human evaluation and its benefits to humans while we admit natural value. Because humans are cultural animals, they know and experience the nature through cultural practices, which determines humans has highest ecological right and duty, and practices eco-ethics in the measure of culture. In this way, Ralston’s theory has constructed ‘earth virtue’ of human subjectivity. In this meaning, Ralston’s theory is essentially a combination of ‘earth ethics’ and ‘earth virtue’.