These four types of associationism share a certain empiricist spiritual similarity, but are logically, and empirically, separable. The pure associationist who wants to posit the smallest number of domain-general mental processes will theorize that the mind consists of associative structures acquired by associative learning which enter into associative transitions and are implemented in an associative instantiation base. However, many hybrid views are available and frequently different associationist positions become mixed and matched, especially once issues of empiricism, domain-specificity, and gradual learning arise. Below is a partial taxonomy of where some well-known theorists lie in terms of associationism and these other, often related doctrines.