Final answer:
The appeal to nature is a fallacy because it incorrectly assumes that something natural is inherently good or right, failing to distinguish between descriptive and prescriptive statements.
Step-by-step explanation:
The appeal to nature is considered a fallacy because it erroneously suggests that something is good or right simply because it is natural. This type of reasoning is problematic because it confuses factual statements (what is) with prescriptive statements (what ought to be). For example, just because certain animals engage in non-monogamous relationships, it does not mean that monogamy or non-monogamy in humans is inherently good or bad.
The challenge of separating facts from values is highlighted in the classic is-ought problem, as articulated by David Hume. Hume and other philosophers like G. E. Moore have pointed out that concluding what is ethical based on natural observations lacks a logical basis, and this mistake is known as the fallacy of relevance.
Furthermore, just because humans are affected by natural laws and often flourish when cooperating with nature does not justify using natural processes as a benchmark for morality or ethics. In philosophy, it's recognized that not everything is as it seems and that logical arguments require stronger foundations than mere observations of natural states or behaviors.