The 9th Amendment was put there in order to guarantee that the government would not infringe natural rights just because they weren't already mentioned in the Constitution. Free speech, freedom of religion, and self-defense are natural rights, and if they hadn't already been mentioned, they would be guaranteed by this amendment.
It is interesting to think of other rights which this amendment guarantees. For instance, the right to eat or ingest whatever we choose. The right to bear children. The right to travel freely on public lands. The right to keep the fruits of our labor. The right to privacy. The right to pursue any occupation we desire, without hindrance. The right to barter in trade. The right to seek any medical treatment we choose.
This is a very valuable amendment, and one which stands in our defense against all kinds of possible abuses by government.
