Sound Deductive Argument

A sound deductive argument is a valid deductive argument whose premises are all true.

• Example(s):
  • All humans are mortal and Socrates is a human so Socrates is mortal.
  • …
• Counter-Example(s):
  • an Unsound Deductive Argument, such as: All organisms with wings can fly. Penguins have wings. Therefore, penguins can fly.
  • a True Conclusion.
• See: Inference Task.

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References

2009

• (Wikipedia, 2009) ⇒ http://en.wikipedia.org/wiki/Argument#Soundness
  • A sound argument is a valid argument with true premises. A sound argument, being both valid and having true premises, must have a true conclusion. Some authors (especially in earlier literature) use the term sound as synonymous with valid.
• (Wikipedia, 2009) ⇒ http://en.wikipedia.org/wiki/Soundness
  • In mathematical logic, a logical system has the soundness property if and only if its inference rules prove only formulas that are valid with respect to its semantics. In most cases, this comes down to its rules having the property of preserving truth, but this is not the case in general.
  • An argument is sound if and only if
    • 1. The argument is valid.
    • 2. All of its premises are true.
  • The following argument is valid but not sound:
    • All organisms with wings can fly.
    • Penguins have wings.
    • Therefore, penguins can fly.
  • Since the first premise is actually false, the argument, though valid, is not sound.

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