This is an example of the paralogism of ‘proving too much’; when a disputant is so eager to refute an opponent as to lay down, or imply, principles from which an easy inference destroys his own position.  To appeal to a principle of greater sweep than the occasion requires may easily open the way to this pitfall:  as if a man should urge that ’all men are liars,’ as the premise of an argument designed to show that another’s assertion is less credible than his own.

A common form of ignoratio elenchi is that which Whately called the ‘fallacy of objections’:  namely, to lay stress upon all the considerations against any doctrine or proposal, without any attempt to weigh them against the considerations in its favour; amongst which should be reckoned all the considerations that tell against the alternative doctrines or proposals.  Incontestable demonstration can rarely be expected even in science, outside of the Mathematics; and in practical affairs, as Butler says, ’probability is the very guide of life’; so that every conclusion depends upon the balance of evidence, and to allow weight to only a part of it is an evasion of the right issue.

Sec. 8.  Fallacies in the connection of premises and conclusion, that cannot be detected by reducing the arguments to syllogistic form, must depend upon some juggling with language to disguise their incoherence.  They may be generally described as Fallacies of Ambiguity, whether they turn upon the use of the same word in different senses, or upon ellipsis.  Thus it may be argued that all works written in a classical language are classical, and that, therefore, the history of Philosophy by Diogenes Laertius, being written in Greek, is a classic.  Such ambiguities are sometimes serious enough; sometimes are little better than jokes.  For jokes, as Whately observes, are often fallacies; and considered as a propaedeutic to the art of sophistry, punning deserves the ignominy that has overtaken it.

Fallacies of ellipsis usually go by learned names, as; (1) a dicto secundum quid ad dictum simpliciter.  It has been argued that since, according to Ricardo, the value of goods depends solely upon the quantity of labour necessary to produce them, the labourers who are employed upon (say) cotton cloth ought to receive as wages the whole price derived from its sale, leaving nothing for interest upon capital.  Ricardo, however, explained that by ’the quantity of labour necessary to produce goods’ he meant not only what is immediately applied to them, but also the labour bestowed upon the implements and buildings with which the immediate labour is assisted.  Now these buildings and implements are capital, the labour which produced them was paid for, and it was far enough from Ricardo’s mind to suppose that the capital which assists present labour upon (say) cotton cloth has no claim to remuneration out of the price of it.  In this argument, then, the word labour in the premise is used secundum quid, that is, with the suppressed qualification of including past as well as present labour; but in the conclusion labour is used simpliciter to mean present labour only.