Thus, the distinction between causality and correlation is an important consideration. This theory approaches two methods of inquiry including locus of causality and stability. Any theory that would allow time travel would introduce potential problems of causality. These studies were widely criticized as showing correlation, not causality. Many types of modeling implicitly involve claims about causality. The standing of causality for quantum mechanics is disputed. Ideally, the relationships express causality, not just correlation. There is no specification of dependent variables, independent variables, or causality. It also makes conclusions about the direction of causality difficult. Even epidemiology is maturing to heed the severe difficulties with presumptions about causality. The social sciences have moved increasingly toward a quantitative framework for assessing causality. There are studies that prove that languages shape how people understand causality. Conditional statements are "not" statements of causality. Basic principles of common sense physics, causality, intentions, etc. These included fundamental structures of space, time, and causality.