Kvod ha Rav, My sincere gratitude and appreciation for giving and sharing these wonderful shiurim! May I suggest another possible answer to the Rashba's question of why one brings an Asham Talui according to Rambam even though he holds safek d'oraysa is permitted min ha torah. It relates to the gavra/cheftza distinction in the shuir, but I'd like to go further and assume for Rambam even a safek issur kares is a permitted action min hatorah. However, even though the action is permitted, if the cheftza is in reality a cheftza of chelev then it is still spiritual "poison", as you analogized it. Whether an act is permitted or not depends on my state of knowledge. It's technically permissible for me to eat this item min hatorah if I am unsure of its kashrus, just as it is clearly permissible for me to eat it min hatorah if I believe it is kosher. However, either way, in reality it might in fact be chelev. If for example I believed b'shogeg it was kosher and find out later it was definitely chelev/"poison", then even though my action at the time was mutar and my after-the-fact knowledge doesn't change that, I do bring a chatas for purification from the reality of having experienced what we now know was a cheftza of issur/poison. Likewise if I just find out later that it was safek chelev, then I bring an asham talui for conditional purification of having *possibly* experienced a cheftza of poison. In other words: my after-the-fact knowledge is not relevant to the halachic permissibility of my action as a gavra. At the time of the act, I thought it was kosher or only safek issur, and if I ask a question min hatorah the answer at that point is yes you may eat it. That is what Rambam means when he says sfeikos only worry us mi-d'rebanan. (Doesn't mean it is wise advice to eat safek issuei kares min hatorah, just that technically it was not forbidden.) Discovering later that it is vadai assur doesn't change the fact that the action I did was literally mutar based on my knowledge at the time of the act. However, I do now know the reality of the cheftza (its "poisonous" quality), and that's what is relevant to chiyuv korban chatas, regardless of whether my action as a gavra was permitted. Likewise, discovering after-the-fact that an item I ate was safek chelev is irrelevant to my original action as a gavra, but I am now aware that the cheftza might *possibly* have been poisonous, and that's what matters for chiyuv asham talui. (Some issurei kares other than forbidden foods may perhaps be more centered on action as opposed to objects, but "cheftza" is used here in a broad sense. "Gavra" here refers to the subjective issue of whether conduct is legally permitted for this person under the circumstances, and cheftza is the objective question of whether in reality the physical situation embodied the issur. Perhaps something along those lines was intended in the shiur as well?) With great respect, esteem and thanks, Steven (Shalom)