Critics of TSSI, including David Laibman (see Criticism section below), argue that Marx intended to present what they characterize as "a structurally consistent" model of value formation in a capitalist economy with competitive profit-rate equalization. They claim that Marx's formulations fail to do this, but also what they characterize as his fundamental insights can be revealed, and extended, by means of models and concepts that emerged after his time. Instead of trying to defend the consistency of Marx's original statements, non-TSSI Marxist theorists pursue what they characterize as ever-more effective versions of what they claim to be the core theory. They also claim that they believe that Marx himself would have done this.