casuistry

The use of clever but unsound reasoning, especially in relation to moral issues; (theology) case-by-case resolution of moral dilemmas.

• casuist/ˈkæʒuɪst/(n)诡辩者
• casuistic/ˌkæʒuˈɪstɪk/(adj)诡辩的

• moral casuistry
• engage in casuistry
• elaborate casuistry
• legal casuistry

1. 1.His argument that lying to protect feelings is always justified was dismissed as casuistry. (specious reasoning)
2. 2.The lawyer's casuistry twisted the law's intent to serve her client's interests. (clever but misleading logic)

• sophistry/ˈsɒfɪstri/— cleverly deceptive reasoning
• specious reasoning /ˈspiːʃəs/ (apparently correct but actually wrong)
• equivocation/ɪˌkwɪvəˈkeɪʃən/— deliberate ambiguity

from Latin "casus" = a case — originally the theological practice of resolving moral dilemmas case by case — later took on negative connotation of twisting logic