 Let’s see how these assumptions lead to a problem in light of the negative singular existence sentence “Pegasus does not exist”. If “Pegasus does not exist” is true, then it must be meaningful (by (1) above). If it is meaningful, all of its constituents must be meaningful, including the singular term “Pegasus” (by (2) above). If “Pegasus” is meaningful, then “Pegasus” denotes something (by (3) above). If “Pegasus” denotes something, then “Pegasus does not exist” is false (by (4) above). Thus, the assumption that “Pegasus does not exist” is true leads to the conclusion that this same sentence is false. So if the above premises are correct, it is impossible that “Pegasus does not exist” is true: either “Pegasus” denotes something, in which case “Pegasus does not exist” is false; or “Pegasus” does not denote anything, in which case “Pegasus does not exist” is not even meaningful, let alone true.