The argument concludes that Aleph is the more cost efficient contractor because its building cost was a substantial percent less than the competition’s, even though its maintenance costs were higher than Gimmel’s, albeit by a smaller percentage. Besides the assumption that the facts are accurate, this argument hinges on several other assumptions of dubious currency. Most strikingly, the argument assumes that a lower percentage automatically indicates a lower numerical cost. This is mathematically untenable. The author merely assumes that the maintenance base price is low enough that a smaller percentage indicates a smaller cost. If this is incorrect, the conclusion becomes erroneous. Furthermore, the argument apparently assumes that the lifespan of these buildings is not long enough for the additional maintenance costs to outweigh the construction savings. A miscalculation here would also completely undermine the conclusion.

While the aforementioned assumptions are certainly enough to question the validity of the conclusion, this argument contains several other quite possibly unwarranted assumptions. First, the author assumes that the contractors’ prices have not changed in the interim. Additionally, the argument states that the buildings are “nearly identical,” but the author only assumes that those implied small differences do not account for the difference in price. Furthermore, the argument takes for granted that the costs of all other features of the buildings — the land, zoning costs, transportation, etc. — were identical. Another unsupported assumption is that the maintenance costs will not change. Similarly, the author blithely relates the higher maintenance costs to the contractor without providing evidence that the costs do not result from unrelated factors. Finally, the argument supposes that there is no other contractor that would prove the least costly of all.

This litany of unsupported assumptions seriously jeopardizes the certainty of the conclusion. If any one of the suppositions contained in the argument proved false, the conclusion would be factually wrong, as Aleph would then not be the most cost efficient option.