The greek for "appoint", apokeimai (ap-ok'-i-mahee) means to be reserved; figuratively to await: - be appointed, (be) laid up. According to this verse alone, this would negate unconditional election and limited atonement. If all men are appointed to die once, this would apply to the reprobate as well as the elect. This would mean that nobody was created for the sole purpose of destruction. If man were created to be reprobate (for destruction), the reprobate would have been appointed "twice" to die, not once.