Technology has changed rapidly over the last few years with touch feedback, known as haptics, being used in entertainment, rehabilitation and even surgical training. New research, using ultrasound, has developed an invisible 3-D haptic shape that can be seen and felt. (1)

You can feel things which are there.
And things which are not.
You may not feel things which are there.
You may not feel things which are not.

Got it?

Related article: Bacteria. Touch Humans.

(from Philosophy Garbage - Harmonia Philosophica circle portal)