The theory of sense data is a view in the philosophy of perception, popularly held in the early 20th century by philosophers such as Bertrand Russell, C. D. Broad, H. H. Price, A. J. Ayer, and G. E. Moore.
These objects are unanalyzed experiences inside the mind, which appear to subsequent more advanced mental operations exactly as they are.
Sense data are often placed in a time and/or causality series, such that they occur after the potential unreliability of our perceptual systems yet before the possibility of error during higher-level conceptual analysis and are thus incorrigible.
One of the greatest troubling aspects of 20th century theories of sense data are their unclear rubric nature.
Sense data theories have been criticised by philosophers such as J. L. Austin and Wilfrid Sellars (the latter most notably in formulating his famous "Myth of the Given" argument), and more recently by Kevin O'Regan, Alva Noë and Daniel Dennett.
More recent opposition to the existence of sense data appears to be simply regression to naïve realism.
By objectifying and partially externalising a subject's basic experiences of the world as 'sense-data', positing their necessity for perception and higher order thinking and installing them permanently between the perceiving subject and the 'real world', sense-data theories tend towards solipsism.