_Simple Constructive_. Celarent or Ferio. If A is B or if E is F, C is not D No cases of either A being B or E being F are cases of C being D. Either A is B or E is F. All (or some) actual cases are cases of either A being B or E being F .'. C is not D. .'. All (or some) actual cases are not cases of C being D. CHAPTER XXVIII. _Of the Dilemma regarded as an Immediate Inference._ § 798. Like the partly conjunctive syllogism, the dilemma can be expressed under the forms of immediate inference. As before, the conclusion in the constructive type resolves itself into the subalternate of the major itself, and in the destructive type into the subalternate of its contrapositive. The simple constructive dilemma, for instance, may be read as follows-- If either A is B or E is F, C is D, .'. Either A being B or E being F, C is D, which is equivalent to Every case of either A being B or E being F is a case of C being D. .'. Some case of either A being B or E being F is a case of C being D. The descent here from 'every' to 'some' takes the place of the transition from hypothesis to fact. § 799. Again the complex destructive may be read thus-- If A is B, C is D; and if E is F, G is H, .'. It not being true that C is D and G is H, it is not true that A is B and E is F, which may be resolved into two steps of immediate inference, namely, conversion by contraposition followed by subalternation-- All cases of A being B and E being F are cases of C being D and G being H. .'. Whatever is not a case of C being D and G being H is not a case of A being B and E being F. .'. Some case which is not one of C being D and G being H is not a case of A being B and E being F. CHAPTER XXIX. _Of Trains of Reasoning._ § 800. The formal logician is only concerned to examine whether the conclusion duly follows from the premisses: he need not concern himself with the truth or falsity of his data. But the premisses of one syllogism may themselves be conclusions deduced from other syllogisms, the premisses of which may in their turn have been established by yet earlier syllogisms. When syllogisms are thus linked together we have what is called a Train of Reasoning.