thoughtlessness (n.)

• abandon
• absentmindedness
• asininity
• buffoonery
• callowness
• caprice
• carelessness
• casualness
• childishness
• crankiness
• craziness
• disregard
• distraction
• easiness
• eccentricity
• fatuity
• fatuousness
• fecklessness
• flightiness
• flippancy
• folly
• foolery
• foolishness
• forgetfulness
• frivolity
• frivolousness
• giddiness
• hastiness
• heedlessness
• idiocy
• imbecility
• immaturity
• improvidence
• imprudence
• inability
• inadequacy
• inadvertence
• inadvertency
• inadvisability
• inanity
• inaptitude
• inaptness
• inattention
• inattentiveness
• incapability
• incapacity
• incompetence
• incompetency
• inconsiderateness
• inconsideration
• indifference
• indiscreetness
• indiscretion
• ineffectiveness
• ineffectuality
• inefficiency
• ineptitude
• ineptness
• inexpedience
• injudiciousness
• insanity
• insouciance
• irrationality
• laziness
• levity
• lunacy
• madness
• maladjustment
• maladroitness
• mediocrity
• mindlessness
• negligence
• nonobservance
• oblivion
• obliviousness
• pompousness
• puerility
• queerness
• recklessness
• rustiness
• senselessness
• shallowness
• shiftlessness
• silliness
• stuffiness
• stupidity
• superficiality
• tactlessness
• thriftlessness
• triviality
• unawareness
• unconsciousness
• unfitness
• unhelpfulness
• unmindfulness
• unreason
• unskillfulness
• unsoundness
• unthoughtfulness
• unwariness
• unwiseness
• volatility
• weirdness