If you were having a stroke from arial fib would you know beyond a shadow of a doubt?

Severity? : Stroke from any cause, including af, can occur in any severity from very mild to very severe. A person who suddenly lost the ability to speak and is paralyzed in the right arm and leg would probably notice something is up. A person with a little haziness of thought for 20 minutes might not.

Not specifically: The person with a stroke in evolution (tia or cva or bleed) may not recognize the situation and that's why aha has encouraged knowledge of the signs. Similar stroke symptoms may be related to carotid disease, heart disease, atrial fibrillation and high blood pressure.

Stroke is a stroke: There are many causes for a stroke, which manifest as a sudden loss of neurological function in some part of the brain. However, there are many causes: you could have a stroke from a clot that forms in the brain (ischemic stroke), from a clot that moved from the heart (as in atrial fibrillation), from a plaque in the neck (carotid artery disease). They'd all feel and look the same.

Likely: Beyond a shadow of a doubt is a term that is seldom used in medicine. As previously answered a stroke may come from multiple sources, including the heart. New numbness, speech difficulty, weakness associated with "a hamster running around in your chest" is suggestive of a heart source.