That's not true. When you predict that something will happen, and it does, this does not mean that the thing is deterministic. This conclusion would require a further premise which states that something can only be predicted if it's deterministic. — Metaphysician Undercover

No it doesn't. It requires a definition of determinism that implies prediction-making.

https://www.merriam-webster.com/dictionary/determinism

Determinism: a theory or doctrine that acts of the will, occurrences in nature, or social or psychological phenomena are causally determined by preceding events or natural laws.

Predictions can only be made if occurrences that we observe are consistently determined by prior causes. If they aren't then we can't make predictions. Because they are consistent, we can make predictions both forward and backwards in time. We can predict the causes of some occurrence or predict the occurrence of some causes. Because the causal relationship is consistent, we can predict the cause or the occurrence. If it weren't we could never establish any kind of reliable predictions for very long. Our knowledge would be even less reliable than it is now - to the point of being useless.

Neither is this true. Minds can predict things which are not deterministic by many different means, like chance, by some system of statistics and probabilities, or through vagueness in terms . I can predict the outcome of a coin toss. If I am right, I've successfully made the prediction. I can also predict that if I flip the coin 100 times half will be heads and half tails. If the score is 51 to 49 I can employ vagueness to claim that it's close enough to count as half and half, therefore my prediction was correct. For a prediction to be correct, it is not required that the thing predicted is deterministic, nor that the thing follows any logical pattern, it only requires a successful strategy by the predictor. — Metaphysician Undercover

Chance and probabilities are ideas in the mind that relate to our lack of knowledge of some system. When we use these terms, we are emphasizing that we don't fully understand the causal relationships, or that the causal relationships are too complex, or there is too much information involved for our minds to make predictions about. This is one purpose that we have given computers - create simulations with massive amounts of information of causal relationships so that we may better predict the behavior of hurricanes.

No it doesn't. It requires a definition of determinism that implies prediction-making. — Harry Hindu

Right, the faulty definition of "deterministic", which you added is the premise required. It's a false premise though because it's not an acceptable definition of "deterministic".

Predictions can only be made if occurrences that we observe are consistently determined by prior causes. — Harry Hindu

This is not true though, as I explained, a prediction could be made randomly and be correct by chance. Or, a prediction could be made using many other strategies, some of which I described, without the need for determinism. That the actions of a human being may sometimes be correctly predicted does not prove determinism, nor disprove free will, which would be the case if prediction could only be made when actions are predetermined.

I think you are assuming "prediction" which has absolute infallibility, no chance of failure. This might require a deterministic system, but human prediction is unable to obtain such perfection. So, determinism is not required for a correct prediction.