Examples of various approaches are primordialism, essentialism, perennialism, constructivism, modernism, and instrumentalism. Popper contrasts instrumentalism with the above mentioned essentialism and his own "critical rationalism". If his essentialism is false, then so too is his ground for disallowing relativism. But Goldman has argued that this association between veritistic epistemology and essentialism is not necessary. Critics have accused Jung of metaphysical essentialism. Thus, gender bending protests gender essentialism. Difference feminism did not require a commitment to essentialism. This gender essentialism is consistent with the Jungian philosophy undergirding the movement. Jung's staunchest critics have accused him of either mystical or metaphysical essentialism. The performance of gender reinforces the essentialism of gender categories. Furthermore, the essentialism of gender in feminist theory presents a problem when understanding transfeminism. Karl Popper splits the ambiguous term "realism" into "essentialism" and "realism". He argues for a form of scientific essentialism not unlike Aristotelian essentialism. This perspective is a criticism of the essentialism of philosophical modelling studies. Alternatives to gender essentialism were proposed in the mid-20th century.