David Hume attempted to study human nature by using the laws of physical science. He also set out to find an absolute truth by using scientific reasoning. In his search for an absolute truth he discovered an immense difference among opposing opinions on nearly every subject confronted by man. Each of these opinions has an equal truth-value and there is really no way of justifying any one over the other because the truth is different for each individual. The sequence of events that each person has experienced throughout their life depicts how they will interpret things and because no two people experience the same exact events throughout their life no two people will interpret the same things from what they perceive from their senses. When it comes to things like this that are matters of fact, there will never be a case where everyone is in agreement. Their will always be disagreements over the validity of everything because the "truth" is only how different people comprehend the things they perceive through their senses. Therefore using any type of scientific method was useless in proving certainty of human nature because there would always be enough evidence to prove the opposing view as being the truth. However the truth can be proved when referring to the relations of ideas. When dealing with things like (2+2=4), there is no openness to interpretation and no exceptions. 2+2 must always = 4 because it is based on scientific factual information and there is clearly no argument against it.

             Hume boldly states that "impressions" and "ideas" make up the total content of the mind. His definition of 'impressions" is what each person perceives from the physical world through their senses. And according to this theory "ideas" are merely copies of these impressions within the mind. He justifies this by saying that when we imagine something that we have never actually seen before our minds are actually transposing impressions that we have formerly perceived and rearranging them in a new way.