Your notebook, your phone and your mind might be one single thinking system

Philosophers Andy Clark and David Chalmers argued that when a tool is reliably available, trusted and used as automatically as biological memory, it becomes genuinely part of your cognitive process, not just an aid to it. Their example: a man with memory loss who writes everything in a notebook and consults it as unreflectively as anyone consults their own recollection is, functionally, remembering with the notebook. On this view, where your mind ends isn't fixed at your skull.

— Andy Clark and David Chalmers, The Extended Mind — Analysis, Vol. 58, No. 1, 1998