Got this game yesterday and loving it, got most of my questions out of the way by reading the general/rules forum about any clarifications I needed. One still eludes me though.
There are some cards like "Sheep Shearer" that give you a benefit if you have in the case of the shearer 1/2/3 wool if you have 3/6/9 sheep. What happens if you don't have any sheep? Can you still play the card to get the points? You don't have to pay a cost like some of the other cards so, does it just give you 0 wool if you have 0-2 sheep and 2 points?
The appendix states, "When you play this card, if you have at least 3/4/6 sheep, you immediately (and only once via this card) receive 1/2/3 wool, respectively."
I would argue that since it says "if", that benefit is optional. You would get the points and receive no wool.
As a side note, the rules DO say you have to use at least one of the "effects" of an action space (paying a cost and/or getting at least one benefit from the space), but I am guessing cards are different.