Nothing Is certain except inaction also has consequences
Big choices in life seldom are made with certainty. They have to be made based on assessments of likely outcomes. The "I'm not going to take action because it might have bad consequences attitude" is no sign of moral rectitude when inaction may result in worse consequences. Sure we don't know the outcome if we had not invaded Iraq, but it is rather silly to predict a radical change in direction with absolutely zero evidence.