The naturalist fallacy is when you jump from describing something as true to saying that it should be done. In his work, David Hume wrote that “Reason is the slave of passion”. His work was influential in making us question whether we can trust our emotions. For example, when we say “murder is wrong”, it might mean something different from what you think it means. If you are emotionally against murder, then your conclusion will likely be “murder is bad”. But if you are emotionally pro-murder, then your conclusion will probably be “murder is right”. So, according to Hume, our conclusions depend on our feelings. He argued that the same is true for moral philosophies when philosophers jump from describing something with ‘is’ and shift to ‘ought’ as they go deeper into the philosophical tandem. The naturalistic fallacy in moral philosophy raises more questions and denies how philosophers present subjective opinions as objective realities.
In the 20th century, A.J Ayer’s theory of emotivism – or the boo hurrah theory – took this further. Emotions aren’t facts, he argues. Emotion doesn’t tell us anything at all about reality. We feel things because they are pleasant or unpleasant. Our emotions come first, and the truth second. The moral proposition “Murder is wrong” looks like a statement of objective fact, but is really an emotional appeal that states “Murder? Boo!”. And the moral proposition “Philanthropy is good” seems like a statement of objective truth, but is really an appeal to get others to agree with you.
