Analysis, personal thoughts, reflection, reports of conversations,
listings of confusions, notes on connections you've made with other
areas of life -- anything that demonstrates your engagement with the
material, your trying to understand it or lend support to it or refute
it. The entires need not be profound -- it is not worth skimming the
internet to find some awesome criticism to plagiarize. The journals
are not graded on profundity. They are graded on the basis of whether
they are complete, submitted on time, and show some effort to think
about the material outside of the classroom (whatever that effort might
amount to).