 Today a lack of agreement remains over the ultimate philosophical contribution of Principia, with some authors holding that, with the appropriate modifications, logicism remains a feasible project. Others hold that the philosophical and technical underpinnings of the project remain too weak or too confused to be of great use to the logicist. (For more detailed discussion, readers should consult Quine 1963, 1966a, 1966b; Landini 1998, 2011; Linsky 1999, 2011; Hale and Wright 2001; Burgess 2005; Hintikka 2009; and Gandon 2012.)