Hi!
This is the second attempt of congratulating Dewey Dykstra for his message.
About telling lies to students and telling them that you tell them lies,
and that you tell them that you tell them so, and such nonsense. I
think that the correct thing is to be careful with the words you use.
Tell them that if we out a hot and a cold body in thermal contact, we
observe that everything HAPPENS AS IF "heat" would be some fluid,
flowing from the hot to the cold body. Actually, nobody can observe
anything flowing, and the only observation is that the hot body gets
cooler and the cold body get warmer! But you don't tell them that
heas IS A FLUID and flows to the right or to the left. Just that in
a (very restricted) class of processes, one can argue this way and
obtain correct results. Later on you will find processes where this
type of argument is incorrect, for example when friction makes appear
heat out of nowhere. In electricty we have a similar situation: when
dealing with electric current EVERYTHING HAPPENS AS IF the electricity
would be some fluid flowing through conducting materials, from the
places of higher potential to lower potential. So you avoided telling
any lies!
Regards Emilio