act of God in law, an accident caused by the operation of extraordinary natural force. The effect of ordinary natural causes (e.g., that rain will leak through a defective roof) may be foreseen and avoided by the exercise of human care; failure to take the necessary precautions constitutes negligence , and the party injured in the accident may be entitled to damages. An act of God, however, is so extraordinary and devoid of human agency that reasonable care would not avoid the consequences; hence, the injured party has no right to damages. Accidents caused by tornadoes, perils of the sea, extraordinary floods, and severe ice storms are usually considered acts of God, but fires are not so considered unless they are caused by lightning.