cogito ergo forsit sum
[and so, and so, and yet and yet...]

And now I see with eye serene,
The very pulse of the machine;
A being breathing thoughtful breath,
A traveller betwixt life and death;

Wordsworth, She Was A Phantom of Delight (1807)

An almost completely open source 3.5 year old (size not age) nascent humanoid robot called the iCub will soon be better equipped to touch the human chord with pressure-sensitive skin. An 'i' that does not refer to Steve Jobs or its own metaphysical ego, the Cub is funded by the European Commission to investigate cognition especially in relation to tactile awareness and intelligence.

The world of dew
is the world of dew,
and yet and yet...

Kobayashi Issa

In the 18th Century, an aged woman recovered from a stroke. Upon regaining the ability to speak she reported to her caregivers that she was, in fact, dead. She compelled daughter and servants both to conduct her final service and upon their doing so, she laid her shrouded self in the coffin and fell asleep. She was not, in fact, dead and upon awakening, which she indeed did, she felt the same, that is to say, she felt that she was dead.
Cotard's Delusion or, affectionately but I feel not euphemistically, Walking Corpse Syndrome is a rare psychiatric disorder in which a person believes that they do not exist, are dead, rotting or missing blood and internal organs.
And so. Where does that leave Descartes' irrefutable truth? Will there exist a world in which the breathing do not exist and the bot breathes thoughtful breath, both all too fully betwixt life and death?

And so, and so. A man has a motor accident and wakes up to find that a woman is crying on his cheek. She smells familiar, but something is wrong. He touches her papery cheek and she looks up and smiles. The man feels something awry in that smile. She looks like his mother, and yet and yet...

The related Capgras syndrome is embodied in feelings that one's beloveds are impostors. It is believed to be the result of a breakdown within the brain between the area that processes visual information, such as faces, and the limbic or emotional system. The Fregoli Delusion is where one believes that different people are in fact the same the same person in disguise.

Often people with Capgras/Fregoli have psychotic disorders. Some merely have brain damage from accidents or strokes. Doctors used to believe that psychotics spun around in a chair would not get dizzy when a sane person would. Not as bad as being drowned or burnt to prove your innocence on witchcraft charges, but motion sickness as proof of sanity seems ineffectual and unsavoury to say the least.

Lesions on the fusiform gyrus, the part of the brain that recognises bodies and faces can damage its ability to connect to other parts of the brain. She looks like his mother but no emotions arise when he sees her, so she seems an impostor. Often the 'impostor' can leave the room, call the affected on the telephone and once again be recognised. Upon re-entering, they become 'imposter' once again. This is because the auditory recognition system is separate in the brain, according to V. S. Ramachandran, my personal favourite neuroscientist and all-around polygonal chap. The TED talks and in fact anything by Ramachandran is well worth looking into.