logic first exam

how to know if an argument is valid

-An argument is valid if the premises can't all be true without the conclusion also being true. -An argument is valid if the truth of all its premises forces the conclusion to be true. -An argument is valid if it would be inconsistent for all its premises to be true and its conclusion to be false. -An argument is valid if its conclusion follows with certainty from its premises. -An argument is valid if it has no counterexample, that is, a possible situation that makes all the premises true and the conclusion false.

cogent argument

A cogent argument is an inductive argument that is strong and has all true premises.

Deductive reasoning/argument

A deductive argument is an argument that is intended by the arguer to be deductively valid, that is, to provide a guarantee of the truth of the conclusion provided that the argument's premises are true. This point can be expressed also by saying that, in a deductive argument, the premises are intended to provide such strong support for the conclusion that, if the premises are true, then it would be impossible for the conclusion to be false.

define a sound argument

A sound argument is a deductive argument that is valid and has all true premises.

define argument

An argument, in its simplest form, is a group of statements, one or more of which (the premises) are claimed to provide support for, or reasons to believe, one of the others (the conclusion). Every argument may be placed in either of two basic groups: those in which the premises really do support the conclusion and those in which they do not, even though they are claimed to.

example of a mildly strong deductive argument

Every time I've walked by that dog, it hasn't tried to bite me. So, the next time I walk by that dog it won't try to bite me.

inductive reasoning/argument

Inductive reasoning makes broad generalizations from specific observations. The premises of an inductive logical argument indicate some degree of support (inductive probability) for the conclusion but do not entail it; that is, they suggest truth but do not ensure it. Unlike deductive arguments, inductive reasoning allows for the possibility that the conclusion is false, even if all of the premises are true

example of a valid deductive argument

It's sunny in Singapore. If it's sunny in Singapore, then he won't be carrying an umbrella. So, he won't be carrying an umbrella.

define logic

Logic may be defined as the organized body of knowledge, or science, that evaluates arguments.

how to test for validity example

To test an argument for validity we begin by assuming that all the premises are true, and then we determine if it is possible, in light of that assumption, for the conclusion to be false. Here is an example: All television networks are media companies. NBC is a television network. Therefore, NBC is a media company. In this argument both premises are actually true, so it is easy to assume that they are true. Next we determine, in light of this assumption, if it is possible for the conclusion to be false. Clearly this is not possible. If NBC is included in the group of television networks (second premise) and if the group of television networks is included in the group of media companies (first premise), it necessarily follows that NBC is included in the group of media companies (conclusion). In other words, assuming the premises to be true and the conclusion false entails a strict contradiction. Thus, the argument is valid.

what is an invalid deductive argument

arguments in which the conclusion is completely false but the premises are true

Either Albany is the capital of New York or it is the capital of Pennsylvania. But Albany is not the capital of New York. Therefore, Albany is the capital of Pennsylvania.

deductive and valid

A statement may legitimately be spoken of as ''valid'' or ''invalid.''

false

An argument may legitimately be spoken of as ''true'' or ''false.''

false

If an argument has true premises and a true conclusion, we know that it is a perfectly good argument.

false

Invalid deductive arguments are basically the same as inductive arguments.

false

Some arguments, while not completely valid, are almost valid.

false

a sound argument may be invalid

false because a sound argument is one where it is valid and all of the premises are true

validity

if we assume the premises are true it follows that the conclusion is true the premises could be false but still a valid statement

what is an invalid deductive argument

invalid deductive argument is a deductive argument in which it is possible for the conclusion to be false given that the premises are true. In these arguments the conclusion does not follow with strict necessity from the premises, even though it is claimed to.

Erik Erikson wrote that human life as the individual experiences it is produced by the interaction and modification of three major systems: the biological system, the psychological system, and the social system. Each system can be examined for patterns of continuity and change over the life course. Each system can be modified by self-guided choices. The integration of the biological, psychological, and social systems leads to a complex, dynamic portrait of human thought and behavior.

non argument

If doctors are right that lifestyle is largely responsible for the increased incidence of diabetes, osteoporosis, heart disease, and strokes, then a mere change in lifestyle would reduce the incidence of these diseases, it would bring the cost of healthcare under control, and universal healthcare would not bankrupt the federal treasury as it currently threatens to do.

non argument

argument or not? Traditionally patients have been viewed as ignorant about medical matters, fearful about being sick, and childlike by virtue of their illness. They are ill-equipped to sort out what is in their best medical interest and prone to make decisions detrimental to their welfare. Thus physicians have asserted that it makes little sense to consult patients on treatment options; far better to interact with them as beloved children and decide for them.

non argument

strong inductive argument

strong inductive argument is an inductive argument in which it is improbable that the conclusion be false given that the premises are true. In such arguments, the conclusion does in fact follow probably from the premises.

A valid argument may have a false premise and a false conclusion.

true

A valid argument may have a false premise and a true conclusion.

true

Inductive arguments allow for varying degrees of strength and weakness.

true

a cogent argument must be inductively wrong

true

a sound argument may have a false conclusion

true

uncogent argument

uncogent argument is an inductive argument that is weak, has one or more false premises, fails to meet the total evidence requirement, or any combination of these.

define an unsound argument

unsound argument is a deductive argument that is invalid, has one or more false premises, or both.

what is a valid deductive argument

valid deductive argument is an argument in which it is impossible for the conclusion to be false given that the premises are true. In these arguments the conclusion follows with strict necessity from the premises.

weak inductive argument

weak inductive argument is an argument in which the conclusion does not follow probably from the premises, even though it is claimed to.