If I understand you correctly an appeal to subjectivism would be when a doctor tells you that you’re going to die. He gives you an objective reason showing you the X-rays. he shows you the blood reports. He shows you the chance of survival of what wrong with you and the estimated time you have. But then you ignore the objective and pray earnestly to God for Him to heal you, believing God will. You genuinely believe and hope you are right. Is this an appeal to subjectivism?
Not quite. In my example, I did not want the objective truth, the objective opinion but I recognized it and accepted it. Same with your example.
In your example an Appeal to Subjectivism would be something like, "You can't die. You're too pretty and young." Most people can relate to the feeling of the subject. No one likes to see young people die. Just because something is what we want or don't want, does not make it true.
Understanding logical fallacies (by name) is one of the best things I got out of my undergraduate education. The best example of another fallacy I remember from that time is called False Alternative. The example used was when VP Al Gore defended the Clinton Administration's decision to intercept Haitian refugees and turn them back. (Now contrast that to the open border policy. Because Haitians don't tend to vote Democrat, they do not want more of them here.)
Gore said, "It is cheaper to intercept them than have them come here and be on welfare." While this is true, it is not logical because of the conjunction "and." This makes it seem like there are only 2 choices. We could not spend the resources to intercept them AND not allow them to go on welfare.
So, Appeal to Subjectivism is when one refers to themselves in some manner (explicitly or implicitly) as the basis to forming their opinion.
- Candidate A looks the best (to me). So, I'll vote for Candidate A, who is the best candidate.
- My experience with people from denomination X was all bad and everyone I met from denomination Y were wonderful. Therefore, denomination X is bad and denomination Y is good.
- That person looks like someone I had a bad experience with. Therefore, that person is bad.
This last one reminds me of a powerful and personal story, which I seldom share. In college, I had a job as an X-ray transporter. One day I had to transport a baby who had a broken arm. Protocol was to leave the patient in the hallway for the Technician to get the patient in the order I brought them down. The baby was fusing and a compassionate Tech picked her up. The baby stopped fussing.
The Tech wanted to show everyone the poor baby to everyone in the X-ray office, where I too was standing waiting to bring patients back. I happened to be in the corner, as far from the door as possible. The baby saw me and became hysterical, clawing at the Tech as if desperately trying to get even further away from me.
Everyone knew 2 things. The baby's broken arm was caused by abuse. The abuser looked like me. No one can expect a baby to be logical and no one accused me of abusing the baby. The baby committed an Appeal to Subjectivism. (See example 3 above, again). 35 years later, the memory still haunts me.