Why looking is not enough
What the three cases on the previous page show is that outward observation alone makes it hard to reach a firm agreement about whether something is alive.
Your own list
Before reading on: list the characteristics that could be used to tell living organisms apart from non-living matter. Compare what you write with the list on the next page — what is missing, and what is extra?
Two warnings about any such list
Every characteristic you listed will not be visible in every living unit at every moment. A seed is not growing; a tree does not travel. Yet every living unit expresses one or more of the characteristics outwardly.
The second: there are also cases that cannot be sorted cleanly into living and non-living. They come back at the end of this chapter — above all when the talk turns to viruses.
Not showing a characteristic is not lacking it
A characteristic not being seen and a characteristic not being there are different things. The tissue in the freezer is not respiring; but it has not lost the ability to respire. Keep that distinction in mind for the whole chapter.