Transition Theory provides the theoretical underpinning for many explanations for past population changes and, more importantly, for many population projections. Our paper proves, through the use of symbolic logic, that Transition Theory does not contain principles strong enough to support population projections. Such projections, consequently, must be based upon their author’s intuition rather than a reasoned application of Transition Theory. We follow our proofs with a brief discussion of various ways in which the Theory may be modified. Our emphasis is upon and only upon the logical characters of these modifications.