While "Live long and prosper" has become Star Trek's most recognizable catchphrase, Captain Kirk's declaration in the season 2 episode "Return to Tomorrow"—"Risk is our business"—better encapsulates the franchise's enduring philosophy. This statement, delivered by William Shatner's Kirk, argues that true progress and discovery inherently involve uncertainty and are worth pursuing despite potential dangers.
The episode, which originally aired in February 1968, presents a scenario where Kirk and his crew encounter Sargon, an energy being from an ancient civilization. Sargon requests to inhabit the bodies of Kirk, Spock, and Dr. Ann Mulhall to build new physical forms. Despite reservations from Dr. McCoy and the inherent danger of lending their bodies to unknown beings, Kirk advocates for accepting the risk to gain knowledge from a civilization far more advanced than humanity. He draws parallels between this situation and humanity's own history of exploration, from flight to space travel, asserting that such advancements were never achieved by avoiding risk.
This quote distinguishes Starfleet's mission from organizations driven by conquest or profit. Starfleet's pursuit is knowledge for its own sake. Kirk's argument is not about the thrill of danger, but the necessity of embracing the unknown for the sake of advancement. This optimistic outlook, defined by a willingness to face uncertainty rather than a naive belief in guaranteed success, has become the central tenet of the Star Trek universe. The episode also notably features Diana Muldaur, who would later appear in "Is There in Truth No Beauty?" and join the cast of Star Trek: The Next Generation as Dr. Katherine Pulaski.
The timing of "Return to Tomorrow" is also significant, airing shortly before the Apollo 11 moon landing. At a time when humanity was still proving its capacity for space exploration, Star Trek was already envisioning subsequent steps. Kirk's speech places the Enterprise's mission within a continuum of human exploration, suggesting that future achievements will depend on a courage to venture into the unknown.
While other quotes from The Original Series may be more humorous or widely quoted in popular culture, "Risk is our business" most effectively distills Star Trek's enduring message: that the pursuit of knowledge and the expansion of horizons fundamentally require a willingness to confront the unknown.