In propositional logic, affirming the consequent, sometimes called converse error, fallacy of the converse, or confusion of necessity and sufficiency, is a formal fallacy of taking a true conditional statement (e.g., "if the lamp were broken, then the room would be dark") under certain assumptions (there are no other lights in the room, it is nighttime and the windows are closed), and invalidly inferring its converse ("the room is dark, so the lamp must be broken"), even though that statement may not be true under the same assumptions.
ɪn pɹˌɑːpəzˈɪʃənəl lˈɑːdʒɪk, ɐfˈɜːmɪŋ ðə kˈɑːnsɪkwənt, sˈʌmtaɪmz kˈɔːld kˈɑːnvɜːs ˈɛɹɚ, fˈæləsi ʌvðə kˈɑːnvɜːs, ɔːɹ kənfjˈuːʒən ʌv nəsˈɛsɪɾi ænd səfˈɪʃənsi, ɪz ɐ fˈɔːɹməl fˈæləsi ʌv tˈeɪkɪŋ ɐ tɹˈuː kəndˈɪʃənəl stˈeɪtmənt ˈiː.dʒˈiː., "ɪf ðə lˈæmp wɜː bɹˈoʊkən, ðˈɛn ðə ɹˈuːm wʊd biː dˈɑːɹk"ˌʌndɚ sˈɜːʔn̩ ɐsˈʌmpʃənz ðɛɹˌɑːɹ nˈoʊ ˈʌðɚ lˈaɪts ɪnðə ɹˈuːm, ɪɾ ɪz nˈaɪttaɪm ænd ðə wˈɪndoʊz ɑːɹ klˈoʊzd, ænd ɪnvˈælɪdli ɪnfˈɜːɹɪŋ ɪts kˈɑːnvɜːs"ðə ɹˈuːm ɪz dˈɑːɹk, sˌoʊ ðə lˈæmp mˈʌst biː bɹˈoʊkən", ˈiːvən ðˌoʊ ðæt stˈeɪtmənt mˈeɪ nˌɑːt biː tɹˈuː ˌʌndɚ ðə sˈeɪm ɐsˈʌmpʃənz.