al.' Even if his methodological conjecture is correct, it needs to discover the fact that which causes the problem of undergeneration. Tennant may believe that the CR−rule has the problem of causing a normal derivation of ⊥ and concealing a non-terminating reduction sequence, i.e. a primary feature of the paradoxes. Section 2.3 provides derivations which cause the problem of undergeneration but do not use CR−rule. That is, CR−rule is not the culprit of the undergeneration problem. To find a solution to the problem, Section 2.4 diagnoses what preventing the occurrence of a non-terminating reduction sequence. With some observations, we propose a possible diagnosis that a nonterminating reduction sequence does not occur if a derivation in question includes (i) a major premise which has no reduction process to eliminate it or (ii) a formula having a principal constant which has no reduction procedure to get rid of it. Then, we suggest an additional condition to TCP that a derivation formalizing a genuine paradox only uses harmonious rules. If the suggested condition is acceptable, the condition can solve the problem of undergeneration. Chapter 3 will cover the problem of overgeneration. In particular, Ekman's paradox presented by Schroeder-Heister and Tranchini (2017) will be introduced. Ekman's paradox is not to be considered a genuine paradox because it involves an inadequate reduction process, and so it causes the problem of overgeneration because it is a T-paradox with respect to Tennant's criterion. To begin with, we will see the response of Tennant (2016) to the Ekman's paradox. He argues that if all elimination rules are stated in generalized form, then the problem of overgeneration will be solved. However, in Section 3.2, we will argue that Tennant's response is inappropriate and that the problem of overgeneration will still occur, even if only generalized elimination rules are used. Furthermore, it will be discussed that Tennant's criterion needs to have an additional condition of which reduction pro