Fallacies of presumption occur when an argument has premises that presume what they support to be true. A false dichotomy occurs when a premise give two improbable alternatives but passes them off as the only alternatives available. For example, the argument ‘Either you do your homework now or you’ll procrastinate and never get it done. Therefore, you should do your homework now so you won’t get a bad grade.” This is a presumption (its assuming that by not doing one’s homework right now, the person will inevitably never get it done). Fallacies of ambiguities are arguments with ambiguous premises or conclusions (hence the word ‘ambiguity’). For example, the argument ‘Japan is called the land of the rising sun. Therefore, the land of Japan must belong to the rising sun.” This is an example of an equivocation, because the argument has misinterpreted a symbol (land of the rising sun), for something physical. The rising sun does not own any land, but the phrase ‘land of the rising sun’ implies that the land of Japan is an extension, or a part of, the actual rising sun. Fallacies of illicit transference is an argument that transfers an attribute from the parts to the whole or from the whole to the parts. For example, the argument ‘My skin is tan, therefore the atoms in my body must also be tan’ is an example of division fallacy. I am taking one attribute of the whole (my skin color) and applying it to the parts (the atoms) that make up my skin.
An intensional meaning is one that lists the traits or attributes of a term. For example, the intensional definition of the world ‘turtle’ would be ‘has a shell, is a reptile, has four limbs’ and so on. An extensional definition is one that lists the members of the class that the term denotes. So, for ‘turtles’, the extensional definition would include snapping turtles, sea turtles, and every other member of the turtle family.
Examples of Intensional and Extensional Definitions:
Demonstrative, enumerative and definition by subclass are definitions that are based on extensions. Demonstrative definitions are ones that involve pointing to an object in order to define it. For example, when teaching a baby to speak, a parent may point to an object that way the baby knows which object is named what. A mother may point to a car and say ‘car’, and the mother may point to numerous types of cars (jeeps, vans, trucks) but will say ‘car’ for every one of them. An enumerative definition is one that names the members of the class that the term denotes. So the enumertaive definition of the term ‘author’ would be Ernest Hemingway, John Steinbeck, Hunter S. Thompson etc. A definition by subclass is a definition that names the sub-classes of a term. The word ‘clothing’ means either a sweater, pants, a jacket etc.
Synonymous, etymological, operational and definition by genus and difference are all examples of definitions that are based on intension. A synonymous definition is one that is synonymous with the first term. So a synonymous definition for the term ‘author’ would be ‘writer’. An etymological definition is one that describes the terms ancestry. The word ‘table’ is derived from the Old English word ‘tabule’, and ‘tabule’ was derived from the Latin word ‘tabula’. An operational definition is one that lists experimental procedures which are used to determine the being of a certain thing. An operational definition for ‘freezing’ could be ‘when a liquid is at or below 32 degrees Fahrenheit and has or is turning solid’. A definition by genus and difference is one that names the genus and a difference word of a term. For example, the term ‘window’ would be defined as a transparent (difference) glass (genus).
- A deduction is “an argument incorporating the claim that it is impossible for the conclusion to be false given the premises are true” (Hurley 33). Basically, a deduction, or deductive argument, is one where the premises are true and the conclusion is also true. There is no doubt or error in the conclusion; it must be true. An example of a deduction is “The meerkat is a member of the mongoose family. All members of the mongoose family are carnivores. Therefore, it necessarily follows that the meerkat is a carnivore” (Hurley 33). This is a deduction because the premises are both true, therefore the conclusion is also true, since the premises support the conclusion. An induction, or inductive argument, is one where the claims are improbably true if the premises are true. With inductions, there is a chance that the premises may be true but the conclusion is false. Inductive arguments will sometimes use generalizations or guesses based off the premises rather than an actual fact. So, the difference between inductive and deductive is that deductive arguments have true premises and a true conclusion, whereas inductive arguments have true premises but may or may not have a true conclusion. Generally speaking, deduction uses more descriptive or factual valid reasoning, whereas inductive arguments make generalizations or guesses that create conclusions which may not be true (even the premises are).