  A general quantum mechanical theory is developed for the isomeric excitation
of $^{229}$Th in strong femtosecond laser pulses. The theory describes the
tripartite interaction between the nucleus, the atomic electrons, and the laser
field. The nucleus can be excited both by the laser field and by laser-driven
electronic transitions. Numerical results show that strong femtosecond laser
pulses are very efficient in exciting the $^{229}$Th nucleus, yielding nuclear
excitation probabilities on the order of $10^{-11}$ per nucleus per pulse.
Laser-driven electronic excitations are found to be more efficient than direct
optical excitations.
