What does "I never know" mean?

Question

They plunged even deeper, passing an underground lake where huge stalactites and stalagmites grew from the ceiling and floor. "I never know," Harry called to Hagrid over the noise of the cart, "what's the difference between a stalagmite and stalactite?" "Stalagmite's got an 'm' in it," said Hagrid.

I was wondering what the meaning of the sentence "I never know something" is? Does it mean "I have never been able to know something", or does it mean "I will never know something"? Why has the present simple tense been used in the sentence?

Answer 1

The use of the simple present tense indicates that a statement applies now.

The use of a modifier such as always or never indicates that the statement it modifies universally applies (always) or doesn't ever apply (never). It is usually used to indicate that the statement relates to a habitual or reoccurring state or action.

When different tenses are used with the modifiers always and never, subtly different meanings are implied.

• The simple past tense indicates that the statement applied at all times in the past, or that it universally applies and the past is the most relevant reference point to your statement. It can be used to imply that the statement no longer applies, especially if used with before. E.g. It always did that before. = at all occasions in the past it did something (that), but on the most recent occasion(s) it has stopped doing "that". Universal application can be inferred from context, it is usually used with never and often means that the point at which it could have happened has passed. E.g. I never climbed Everest. = At no point in the past did I climb Everest, and implies that the point at which I could have climbed Everest has passed, so I will also not climb Everest in the future.
• The simple present indicates that it applies at all times in the past and present. It can imply future continuation, but does not necessitate it. E.g. It always does that. = it currently does "that" and did "that" at all times in the past. It implies that it will probably continue to do "that", but leaves the possibility that it may stop doing "that".
• The simple future indicates that it applies at all points in the future, and it usually indicates that it applies at all times past, present and future (but it may not necessarily). E.g. I will never climb Everest = I have not yet climbed Everest, and I will not climb it in the future. If you include the adverb "again" with never, it means that it occurred previously, but will not occur in future. E.g. I will never climb Everest again = I have climbed Everest, but I will not climb it in the future.

So in your example, I never know implies that the situation has come up before, repeatedly, and Harry has not previously known, and still doesn't know.

Answer 2

Here the word "never" indicates a recurring problem. The problem is that "stalactite" and "stalagmite" are similar-sounding words of Greek origin. Because they are foreign, Harry cannot identify their roots or suffixes and so cannot discern the difference in meaning between them. Most English speakers have trouble with these two words.

If Harry had never been informed which is the stalactite and which the stalagmite we might have simply said "I do not know". But by adding "never" he indicates that the question has come up repeatedly, but he has "never" (not even once) known the answer. This is because, even when he has been informed, he has failed to memorize which is which.

Hagrid's answer is a clever comment on the difficulty which these similar Greek words present to the English speaker. When they look at these words they see only a meaningless collection of letters.