Don Ihde called the hypothesis being 'hyped' and referred to clear evidence about the use of optical tools by, ., Albrecht Dürer and Leonardo da Vinci and others. As well the 1929 Encyclopædia Britannica  contains an extensive article on the camera obscura and cites Leon Battista Alberti as the first documented user of the device as early as 1437.  Ihde states abundant evidence for widespread use of various technical devices at least in the Renaissance and . in Early Netherlandish painting .  Jan van Eyck 's 1434 painting Arnolfini Portrait shows a convex mirror in the centre of the painting. Van Eyck also left his signature above this mirror,  showing the importance of the tool. The painting includes a crown glass window in the upper left side, a rather expensive luxury at the time. Van Eyck was rather fascinated by glass and its qualities, which was as well of high symbolic importance for his contemporaries.  Early optical instruments were comparatively expensive in the Medieval age and the Renaissance. 
What then commends Lazerowitz’s (original) definition – the definition whereby metaphilosophy is investigation of the nature (and point) of philosophy? Two things. (1) The two ‘philosophy–of–philosophy’ construals are competing specifications of that definition. Indeed, those construals have little content until after one has a considerable idea of what philosophy is. (2) The equation of metaphilosophy and post-philosophy is narrow and tendentious; but Lazerowitz’s definition accommodates post-philosophy as a position within a more widely construed metaphilosophy. Still: Lazerowitz’s definition does require qualification, since there is a sense in which it is too broad. For ‘investigation of the nature of philosophy’ suggests that any inquiry into philosophy will count as metaphilosophical, whereas an inquiry tends to be deemed metaphilosophical only when it pertains to the essence , or very nature, of philosophy. (Such indeed is a third possible reading of the philosophy-of-philosophy construal.) Now, just what does so pertain is moot; and there is a risk of being too un accommodating. We might want to deny the title ‘metaphilosophy’ to, say, various sociological studies of philosophy, and even, perhaps, to philosophical pedagogy (that is, to the subject of how philosophy is taught). On the other hand, we are inclined to count as metaphilosophical claims about, for instance, philosophy corrupting its students or about professionalization corrupting philosophy (on these claims one may see Stewart 1995 and Anscombe 1957).