impossibility unlikelihood implausibility impracticability inconceivability impracticality ridiculousness unreasonableness unworkability difficulty hopelessness uselessness unlikeliness improbability doubtfulness dubiousness rarity disadvantage certainty reality impotence inability incapacity incompetence stupidity weakness blockage hindrance injury obstruction permanent stop uncertainty doubt dubiety incertitude scepticism skepticism unpredictability advantage definiteness inevitability misfortune plan solution surety truth definite definitive nonevent necessity assurance assuredness confidence sureness certitude conviction positiveness fact information knowledge proof trust safety design determination protection safeguard closing conclusion ending finish solid restriction constraint restraint limit limitation embargo regulation cramp curb adversity catastrophe debacle disaster failure hardship hitch setback trial tribulation affliction burden calamity cataclysm contretemps drawback impediment mischance