Editing Human brain (section)

===The mind===
{{Main |Cognition |Mind}}
[[File:Phineas gage - 1868 skull diagram.jpg|thumb|upright|The skull of [[Phineas Gage]], with the path of the iron rod that passed through it without killing him, but altering his cognition. The case helped to convince people that mental functions were localised in the brain.<ref name=Macmillan/>]]

The [[philosophy of mind|philosophy of the mind]] studies such issues as the problem of understanding [[consciousness]] and the [[mind–body problem]]. The relationship between the brain and the [[mind]] is a significant challenge both philosophically and scientifically. This is because of the difficulty in explaining how mental activities, such as thoughts and emotions, can be implemented by physical structures such as neurons and [[synapse]]s, or by any other type of physical mechanism. This difficulty was expressed by [[Gottfried Leibniz]] in the analogy known as ''Leibniz's Mill'':

{{Blockquote |One is obliged to admit that perception and what depends upon it is inexplicable on mechanical principles, that is, by figures and motions. In imagining that there is a machine whose construction would enable it to think, to sense, and to have perception, one could conceive it enlarged while retaining the same proportions, so that one could enter into it, just like into a windmill. Supposing this, one should, when visiting within it, find only parts pushing one another, and never anything by which to explain a perception.

::— Leibniz, [[Monadology]]<ref>{{cite book |author=Rescher, N. |title=G. W. Leibniz's Monadology |year=1992 |publisher=Psychology Press |isbn=978-0-415-07284-7 |page=83}}</ref>}}

Doubt about the possibility of a mechanistic explanation of thought drove [[René Descartes]], and most other philosophers along with him, to [[Dualism (philosophy of mind)|dualism]]: the belief that the mind is to some degree independent of the brain.<ref>{{cite book |last=Hart |first=WD |year=1996 |editor=Guttenplan S |title=A Companion to the Philosophy of Mind |publisher=Blackwell |pages=265–267}}</ref> There has always, however, been a strong argument in the opposite direction. There is clear empirical evidence that physical manipulations of, or injuries to, the brain (for example by drugs or by lesions, respectively) can affect the mind in potent and intimate ways.<ref name=Churchland>{{cite book |last=Churchland |first=P.S. |title=Neurophilosophy |publisher=MIT Press |year=1989 |isbn=978-0-262-53085-9 |chapter-url=https://books.google.com/books?id=hAeFMFW3rDUC |chapter=Ch. 8}}</ref><ref>{{cite journal |last1=Selimbeyoglu |first1=Aslihan |last2=Parvizi |first2=J |title=Electrical stimulation of the human brain: perceptual and behavioral phenomena reported in the old and new literature |journal=Frontiers in Human Neuroscience |date=2010 |volume=4 |page=46 |doi=10.3389/fnhum.2010.00046 |pmid=20577584 |pmc=2889679|doi-access=free }}</ref> In the 19th century, the case of [[Phineas Gage]], a railway worker who was injured by a stout iron rod passing through his brain, convinced both researchers and the public that cognitive functions were localised in the brain.<ref name=Macmillan>{{cite book |last=Macmillan |first=Malcolm B. |year=2000 |title=An Odd Kind of Fame: Stories of Phineas Gage |publisher=[[MIT Press]] |url=https://books.google.com/books?id=Qx4fMsTqGFYC |isbn=978-0-262-13363-0}}</ref> Following this line of thinking, a large body of empirical evidence for a close relationship between brain activity and mental activity has led most neuroscientists and contemporary philosophers to be [[Materialism|materialists]], believing that mental phenomena are ultimately the result of, or reducible to, physical phenomena.<ref>Schwartz, J.H. '' Appendix D: Consciousness and the Neurobiology of the Twenty-First Century''. In Kandel, E.R.; Schwartz, J.H.; Jessell, T.M. (2000). ''Principles of Neural Science, 4th Edition''.</ref>