 One of the many attractions of this approach is that it yields a very natural account of what it is to give a causal interpretation to a system of equations of the sort employed in the so-called causal modeling literature. For example, if a linear regression equation \(Y = aX + U\) makes a causal claim, it is to be understood as claiming that if an intervention were to occur that sets the value of \(X=x_0\) in circumstances \(U=u_0\), the value of \(Y\) would be \(y = ax_0 + u_0\), or alternatively that an intervention that changes \(X\) by amount \(dx\) will change \(Y\) by amount \(a\; dx\). As another illustration consider the system of equations