Which type of speech is not protected under the First Amendment?

Defamation is considered unprotected speech under the First Amendment because it involves making false statements that harm a person's reputation. The legal definition of defamation encompasses both slander (spoken defamation) and libel (written defamation). The justification for this is rooted in the idea that individuals have the right to protect their reputations from falsehoods, and courts have established that false statements that damage someone's character do not contribute to the marketplace of ideas that the First Amendment aims to promote.

In contrast, artistic performance, commercial speech, and sacrificial speech have varying degrees of protection under the First Amendment. Artistic performances, which often include forms of expression like music, theater, and visual art, are generally protected as they contribute to cultural and societal discourse. Commercial speech, while more regulated than other types of speech, is still protected to some extent because it provides valuable information to consumers. Sacrificial speech, although less common and less clearly defined, refers to actions that convey a message through symbolic gestures, which can also fall under protected categories of speech depending on the context.