Here is a thought experiment to begin with. You are sitting somewhere reading this. Somewhere in the vicinity is a smartphone. If someone took it away from you, you would feel something recognizable as loss, not just inconvenience, but a genuine diminishment of your capabilities. You would lose access to a significant portion of your memory (contacts, notes, photos, knowledge lookups). You would lose navigational ability. You would lose a major channel of social connection. You would lose the ability to answer most factual questions that arise in conversation.
Now: is the phone part of you? The philosopher Andy Clark and cognitive scientist David Chalmers would say yes, in a philosophically serious sense. Their extended mind thesis (1998) argues that cognition does not stop at the boundary of the skull. When an external device reliably plays the functional role in your cognitive life that an internal brain state would play, when you use it to store information, solve problems, and navigate the world, it is, functionally speaking, part of your cognitive system. The mind, on this view, extends into the world.
If that seems too radical, consider something less exotic. A person with a pacemaker: is the pacemaker part of them? Most people would say yes. A person with a cochlear implant: part of them? Most say yes. A person who has been using GPS navigation for ten years and has lost the ability to navigate without it: has the technology extended their cognitive system, or just atrophied their internal one? The line between tool and part of self turns out to be philosophically fuzzy when you press it.
Donna Haraway's "A Cyborg Manifesto" (1985) takes this further and in a completely different direction. Haraway was not primarily interested in cognitive improvement. She was interested in the political implications of what she saw as an unavoidable fact: the boundary between organism and machine, between natural and artificial, between human and animal, was already collapsing in late 20th century capitalism. Rather than lamenting this collapse or trying to restore the purity of the natural human, she proposed embracing the cyborg, the human-machine hybrid, as a figure of political liberation.
Her argument: the boundaries that were allegedly being violated by cybernetics and biotechnology were never as clean as they seemed, and defending them tended to reinforce oppressive categories. The "natural" woman, the "pure" human body, the "authentic" self, these were never politically innocent concepts. They had been used to police gender, race, and ability in ways that reinforced hierarchy. The cyborg, by blurring these boundaries, potentially disrupts the hierarchies that depend on them.
This is a political and philosophical argument simultaneously, and it is genuinely original. You might agree or disagree with Haraway's politics, but her core observation, that our concept of "human" has always been more constructed, more contested, and more porous than it appears, is philosophically serious and worth engaging with.
Quick reflection
Make a list of the ways technology is currently integrated into your cognitive and physical functioning. GPS, glasses or contacts, medication, social media, search engines, any wearables. Now ask: where does your self end and your technological extensions begin? Is that question meaningful, and does it matter how you answer it?