The Fermi Paradox was proposed during a discussion about whether faster-than-light travel would be developed. Fermi, famously, exclaimed "where are they?" sayin

The Fermi Paradox was proposed during a discussion about whether faster-than-light travel would be developed. Fermi, famously, exclaimed "where are they?" saying that if ftl travel is possible, we should be regularly visited by the numerous alien civilizations that must, statistically, be out there. The Fermi Paradox has come to be the term describing the more general lack of alien detection, but it's only a "paradox" if we expect to be able to detect aliens. That expectation is only reasonable if aliens produce enough activity close enough to us that we would be able to observe it. If FTL is possible, that assumption is an unequivocal yes. Without FTL, it's infinitely more contentious.