PT158 · S2 · Q17 To establish a human colony

This answer says human habitation on Mars will only be feasible if transport costs decrease. The word "only" makes this far stronger than what the argument requires. The argument needs the assumption that Mars cannot supply materials locally — which is one specific reason transport remains necessary. But this answer rules out every possible path to feasibility except decreased transport costs, ignoring alternatives like technological innovations in colony construction, discovery of Mars-based resources, or entirely different approaches. A necessary assumption must be something the argument cannot survive without; this sweeping claim goes well beyond what is needed and introduces constraints the argument never implied.

This answer claims transport costs are "not expected to decrease" in the foreseeable future. The argument does not need this assumption. Even if transport costs were expected to decrease eventually, the argument could still hold if they would not decrease enough, or if the decrease would take too long, or if Mars still could not supply materials locally regardless. The argument's core reasoning is about the current economic infeasibility based on current costs and the absence of local materials. Whether costs might decline in the future is a separate question the argument does not need to address. The necessary assumption is about the availability of Mars-based materials, not about future transport cost projections.

This answer claims Earth is "the only source" of basic materials needed for a Mars colony. While this is in the right conceptual territory — the argument does need to rule out Mars as a source — this answer goes too far by claiming Earth is literally the only source in existence. The argument only needs Mars not to be a practical source. There could be other theoretical sources (asteroids, other moons) that are also impractical; the argument does not need to address them. More precisely, the argument requires that Mars itself cannot supply the materials, not that Earth has a universal monopoly on basic materials throughout the solar system. The necessary assumption is narrower than this answer's sweeping exclusivity claim.

The argument claims Mars colonization is not economically feasible, not that it would produce no significant benefits. An undertaking can have tremendous benefits and still be economically infeasible if the costs exceed those benefits. The argument focuses entirely on the cost side of the equation — the expense of transporting materials — without needing to claim that the benefits are zero. Even if colonizing Mars would yield enormous scientific, strategic, or survival benefits, the argument can still hold if the costs are prohibitively high. This answer addresses a dimension (benefits) that the argument neither discusses nor needs to assume anything about.