Answer
The reason for matter appearing solid is that the naked eye cannot see the variation in the density of matter.
Work Step by Step
Matter appears solid as the variation in the density of matter occurs on such a small scale that it is invisible to the eyes. When one taps a table, it is mostly like one giant movable platform (the finger) that crashes into another (the table). They are both primarily empty spaces, but still do not fall into this category.
