> Slippery slope is not necessarily a fallacy -- it is only a fallacy if the warrant is extreme
It's only a fallacy to suggest that a slippery slope is logically entailed, i.e. to assert without further argument that it's logically necessary for Z to happen if A happens simply because Z is a more extreme form of A.
But slippery slopes certainly do exist empirically, especially with respect to politics, and given the actual nature of a particular political milieu, it can be entirely reasonable to suggest that implementing one policy makes it more likely for a more extreme version of that policy to come about in the future.
> Appeal to authority -- Using the opinion or position of an authority figure, or institution of authority, in place of an actual argument.
Same thing here. As you've said, it's entirely reasonable to apply a heuristic that gives greater credibility to a source whose statements have previously proven useful or valid than one that hasn't.
The fallacy of the appeal to authority is in assuming that a given statement is true because an 'expert' has made it, but it's entirely reasonable to expect that a person you regard as an expert is more likely to make statements that are valid in their own right.
The primary fallacy of those who excessively discuss logical fallacies is the assumption that most arguments actually are applications of deterministic logic intended to assert an unambiguously correct answer to an unambiguous question in the first place. Most arguments really involve the application of heuristics in complex and stochastic contexts, in order to establish an understanding that's marginally more useful than the status quo. Many arguments also involve attempts to reconcile competing conceptions of the desired end state, and are not simply disputes regarding the reasoning applied to obtain a presumptively agreed-upon end state. Formal deductive logic isn't the most relevant template in either of these scenarios.
It's only a fallacy to suggest that a slippery slope is logically entailed, i.e. to assert without further argument that it's logically necessary for Z to happen if A happens simply because Z is a more extreme form of A.
But slippery slopes certainly do exist empirically, especially with respect to politics, and given the actual nature of a particular political milieu, it can be entirely reasonable to suggest that implementing one policy makes it more likely for a more extreme version of that policy to come about in the future.
> Appeal to authority -- Using the opinion or position of an authority figure, or institution of authority, in place of an actual argument.
Same thing here. As you've said, it's entirely reasonable to apply a heuristic that gives greater credibility to a source whose statements have previously proven useful or valid than one that hasn't.
The fallacy of the appeal to authority is in assuming that a given statement is true because an 'expert' has made it, but it's entirely reasonable to expect that a person you regard as an expert is more likely to make statements that are valid in their own right.
The primary fallacy of those who excessively discuss logical fallacies is the assumption that most arguments actually are applications of deterministic logic intended to assert an unambiguously correct answer to an unambiguous question in the first place. Most arguments really involve the application of heuristics in complex and stochastic contexts, in order to establish an understanding that's marginally more useful than the status quo. Many arguments also involve attempts to reconcile competing conceptions of the desired end state, and are not simply disputes regarding the reasoning applied to obtain a presumptively agreed-upon end state. Formal deductive logic isn't the most relevant template in either of these scenarios.