Whilst learning the sugya of piggul there is one matter that is worrying
me intensely.
The Machshava of the Kohen renders the korban posul.
However, if the Kohen was so unscrupulous to have these machshovas in the first place
why should he reveal his true kavonahs to the participants! [baalim]
In other words how would the baalim ever know if their korban was posul
or not without the Kohen revealing his true kavanah!
I look forward to your answer.
Machshavos of Kodashim need to be spoken in order to be effective (see Insights to Zevachim 2a). Therefore, it is possible that the Kohen's words were overheard.
In addition, it is possible that the Kohen made a mistake, not realizing that such a thought invalidates the Korban. He did not maliciously attempt to invalidate the Korban.
D. Zupnik
As a follow up what bothers me is what happens. Someone comes from a distance to bring a Korban he spends time and money and then the cohen invalidates it. Even in cases where the korban is accepted. Since the cohen changed the intention (even by mistake) does the baal now have to spend more time and money. Is there no responsibility on the cohen's part.
The Mishnah in Gitin 54b states explicitly that Kohanim who willfully made a Korban become Pigul are liable.
D. Zupnik