The Commens Dictionary

Quote from ‘Letters to F. A. Woods’

A conditional proposition, – say “If A, then B” is equivalent to saying that “Any state of things in which A should be true, would (within limits) be a state of things in which B is true.” It is therefore essentially an assertion of a general nature, the statement of a “would-be.” But when the antecedent supposes an existential fact to be different from what it actually is or was, the conditional proposition does not accurately state anything; and if it conveys any meaning, i.e. if it is calculated to produce any state of mind, in a person who trusts in it, it must be that it establishes a habit in that mind, using the word “habit” in the original sense, as meaning only that the person or thing that has the habit, would behave (or usually behave) in a certain way whenever a certain occasion should arise.