If you were to ask someone if they were alive, chances are, they would probably say "yes." And if you asked them if their cells were alive, again, they would say "yes." However, if you ask someone whether or not cells are alive, as in "do cells count as life?" most people will give you a resounding "no." Ultimately, scientifically, cells are dead matter moved by the laws of the universe.
Why the difference? What separates living matter from dead matter?
Philosophers have been debating what counts as life since...well, for an absurdly long time. But what does science have to say on this? Can we definitively say what is life? If we can, then what are the criteria?
The latest video Kurzgesagt attempts to address some of these questions.
If you are looking for some more tricky questions—what counts as "you"? For example, if you trim your finger nails, you are cutting off a few atoms. However, you are still you. And say you lose your leg in an accident. Yup. Still you. The same could be said for a heart transplant, a skin graft, and the like. But what about your brain?
Let's say that you removed your brain and had it put in a new body; would that new body be you? What if it was entirely mechanical?
If you want to ponder all these crazy questions, head here for a more detailed breakdown.