VALID OR INVALID? Part Two (NOTE: the conclusion is underlined.)
1. Anyone who has been a Peace Corps volunteer has witnessed poverty and desolation.
All who have not witnessed poverty and desolation are not sensitive to human needs.
Therefore, all Peace Corps volunteers are sensitive to human needs. (Px: x is a Peace
Corps volunteer; Wx: has witnessed poverty and desolation; Sx: is sensitive to human
needs)
2. Some unintentional killings are not punishable offenses, because all cases of selfdefense are unpunishable offenses, and some intentional killings are cases of selfdefense. (Ix: x is an intentional killing; Sx: x is a case of self-defense; Px: x is a
punishable offense)
3. Environmentalists purchase only fuel efficient cars. Therefore, Rolls Royces must not
be fuel efficient, since environmentalists do not purchase them. (Fx: x is a fuel efficient
car; Ex: x is purchased by an environmentalist; r: Rolls Royce)
4. If a marriage is based on a meshing of neuroses, it allows no room for growth. If a
marriage allows no room for growth, it is bound to fail. Therefore, if a marriage is based
on a meshing of neuroses, it is bound to fail. (Nx: x is a marriage based on a meshing of
neuroses; Rx: x is a marriage that allows room for growth; Bx: x is a marriage that is
bound to fail)
5. Everyone likes or is liked by someone or other. Therefore, the person that John likes
also likes him. (Lxy: x likes y; j: John) (Note: assume a universe of persons)
6. Physicists are the only scientists who theorize about the nature of time. The scientist
Stephen Hawkins certainly does that. Therefore, he must be a physicist. (Px: x is
physicist; Sx: x is a scientist; Tx: x theorizes about the nature of time; s: Stephen
Hawkins)
7. Whoever wrote the Declaration of Independence had a big impact on civilization.
Thomas Jefferson certainly had that. Therefore, he wrote the Declaration of
Independence. (Wx: x wrote the Declaration of Independence; Cx: x had a big impact on
civilization; j: Thomas Jefferson)
8. John likes everyone at the playground. Adel and Bill are at the playground.
Therefore, John likes Adel and Bill. (Px: x is at the playground; Lxy: x likes y; a: Adel;
b: Bill; j: John)
9. Violinists who play well are accomplished musicians. There are some violinists in the
orchestra. Therefore, some musicians are accomplished. (Vx: x is a violinist; Px: x plays
well; Ax: x is accomplished; Mx: x is a musician; Ox: x is in the orchestra.