noun (n)

• a condition of damage or decay(noun.state)

  Antonym:
  soundness
  

  source: wordnet30
• a misconception that is fallacious and not true or valid(noun.cognition)

  Example:
  The unsoundness of his conclusion was obvious.
  

  source: wordnet30
• not mentally or physically healthy(noun.attribute)

  Example:
  No one can be a poet without a certain unsoundness of mind.
  

  Antonym:
  soundness, wisdom, wiseness
  

  source: wordnet30