insanity

noun

in·​san·​i·​ty in-ˈsa-nə-tē 

plural insanities

1

dated : a severely disordered state of the mind usually occurring as a specific disorder

2

law : unsoundness of mind or lack of the ability to understand that prevents someone from having the mental capacity required by law to enter into a particular relationship, status, or transaction or that releases someone from criminal or civil responsibility

3

a

: extreme folly or unreasonableness

the insanity of violence

His comments were pure insanity.

b

: something utterly foolish or unreasonable

the insanities of modern life

Did you know?

On the Meaning of Insanity

An oft-quoted bon mot (frequently attributed to Albert Einstein, Benjamin Franklin, or a number of other people who probably never said it) is that insanity may be defined as “doing the same thing over and over and expecting different results.” While the job of lexicographers might be easier if they were allowed to use witty sayings instead of precise definitions, such belletristic labors are not within their purview. The straight facts about insanity are these: it has been in use in English since the late 16th century, for the first two hundred years or so carrying only the literal meaning “the condition of being mentally deranged.” In the 19th century it began to take on a looser sense, “extreme folly or unreasonableness.” In modern usage, insanity may be found in both senses: you may tell your brother that trying to skateboard while holding onto a car is "insanity" (in which case you mean that it is extremely foolish) or encounter the stricter original meaning in such contexts as insanity plea.

Synonyms

• aberration
• dementia
• derangement
• lunacy
• madness
• mania
• rage [archaic]

Examples of insanity in a Sentence

She was found not guilty by reason of insanity.

His friends thought his decision to quit his job was pure insanity.

Please, no more violence. It's time to stop this insanity.

the insanities of modern life

Recent Examples on the Web

Weier had been found not guilty by reason of insanity in September 2017, the Associated Press reported at the time. —Samira Asma-Sadeque, Peoplemag, 12 Apr. 2024

Dorsey entered an insanity defense during the trial, with his attorney saying that on the day of the shooting, Dorsey was depressed, paranoid and dealing with significant life changes. —Jade Thomas, The Indianapolis Star, 5 Apr. 2024

Meanwhile, Shi and his legal team were back in court Thursday trying to establish an insanity defense. —Andrew J. Campa, Los Angeles Times, 15 Mar. 2024

Casteel's lawyers argued that his conviction be set aside because his counsel did not argue an insanity defense, while Casteel blamed mental illness during his own trial in 2014. —Kylie Martin, Detroit Free Press, 15 Mar. 2024

What’s that fake Albert Einstein quote about the definition of insanity? —Daniel Kohn, SPIN, 27 Mar. 2024

She was found not guilty by reason of insanity and was committed to a state mental health facility. —Tim Arango, New York Times, 21 Mar. 2024

What qualifies a person as not guilty by reason of insanity, or NGRI, has shifted dramatically over the years. —Molly Langmuir, Rolling Stone, 2 Feb. 2024

While there’s a seemingly fertile idea in watching how an autocracy crumbles from within and without, as unchecked power breeds a kind of insanity, the more cerebral aspects largely get lost in the show’s eccentricities, overwhelming any sense of nuance. —Brian Lowry, CNN, 1 Mar. 2024

Word History

First Known Use

1590, in the meaning defined at sense 1

Phrases Containing insanity

• insanity plea

Kids Definition

insanity

noun

in·​san·​i·​ty in-ˈsan-ət-ē 

plural insanities

1

: the condition of being insane especially when serious enough to keep one from being convicted of a crime or from performing duties required by law

2

a

: extreme foolishness or unreasonableness

b

: senseless conduct

Medical Definition

insanity

noun

in·​san·​i·​ty in-ˈsan-ət-ē 

plural insanities

1

dated : a severely disordered state of the mind usually occurring as a specific disorder

2

law : unsoundness of mind or lack of the ability to understand that prevents one from having the mental capacity required by law to enter into a particular relationship, status, or transaction or that releases one from criminal or civil responsibility

Legal Definition

insanity

noun

in·​san·​i·​ty

1

: unsoundness of mind or lack of the ability to understand that prevents one from having the mental capacity required by law to enter into a particular relationship, status, or transaction or that releases one from criminal or civil responsibility: as

a

: a disease, defect, or condition of the mind that renders one unable to understand the nature of a criminal act or the fact that it is wrong or to conform one's conduct to the requirements of the law being violated

b

: inability to understand and participate in legal proceedings brought against one : incompetence

c

: inability to understand the nature and purpose of a punishment (as the death penalty) to which one has been sentenced

d

: inability to understand the nature and consequences of one's acts (as making a will) or of events, matters, or proceedings in which one is involved see also commitment, durham rule, irresistible impulse test, m'naghten test, not guilty by reason of insanity, substantial capacity test compare capacity, competency, competent, diminished capacity, sanity

2

: the affirmative defense of having acted while insane