Philosophy (and its corollaries in the human sciences such as literary, social and political theory) is distinguished from other disciplines by a more thoroughgoing emphasis on the a priori. Philosophy makes no claims to predictive power; nor does it aim to conform to popular opinion (beyond ordinary intuitions as recorded by ‘thought experiments’). Many philosophers view the discipline’s self-exemption from ‘real world’ empirical testing as a non-issue or even an advantage, in allowing philosophy to focus on universal and necessary truths. (...) This article argues otherwise. The non-instrumentality of philosophical discourse renders it into a collective private language, impairing the discipline’s ability to judge the quality of its own output. The natural sciences and other technical disciplines offer the non-expert ‘windows of scrutiny’ into their respective methodologies, through numerous findings that can be easily and independently tested by amateurs. Such outside scrutiny provides a mechanism of external quality control, mitigating the internal effects of cognitive bias and institutionalised conformity upon the discourses of technical disciplines. In contrast, the conclusions of philosophy are not testable without in-depth knowledge of the methods by which they are arrived at; knowledge which can apparently only be gained through an extensive program of study, in philosophy. This epistemic circularity renders the program (even one of self-study) into a ‘black box’ in which the internal influence of cognitive biases and conformity effects cannot be independently assessed. The black box of philosophy is, in all relevant respects, analogous to the black box of the Cartesian mind that is the subject of Wittgenstein’s private language argument. (shrink)