How many tactical patterns are there in chess?

I recently read from Dan Heisman that there are around 2000 basic tactical patterns (amended, previously said tactics) in chess.

This seems like an awful lot to learn. After doing chess puzzles for about 50 hours, I figured there might be somewhere between 100 and 200 tactics. I guess it depends on how you count them.

There are 56 different puzzle themes listed on this site. But most involves a combination of two or more themes.

Are there really 2000 basic tactics? Has anyone ever defined/listed all of them? How many advanced tactics are there?

Nimzovich in "My System" listed the elements of chess.

https://en.wikipedia.org/wiki/My_System#The_Elements

How does the 8 elements relate to specific tactics?

Pins and Discovered Checks are definitely tactical themes. There are many tactics based on each of those. Others are based on skewers, trapping pieces etc.

Many puzzles are about getting a pawn promoted.

BTW, I have the My System/Chess Praxis double book but most of it is unread as of yet. There are a lot of different opinions on whether or not it is suitable for lower rated players and even whether it is a good book at all. I haven't really been able to decide for myself.

#3
Also 7th rank, 8th rank, passed pawn...
Opinions differ. Read it and decide for yourself.

The oxford companion to chess has listed 1327 opnening moves and variants alone. There must be many tactics per opening move, so the number creeps towards infinity

There is a new Vox Explained episode on chess which says there are 9 million possible positions after the first 3 moves and 915 billion two or three moves later.

Tactics are grouped by a common idea or concept, like promoting a pawn to a Queen for example is the strongest move in the majority of positions where the pawn is on the 7th rank and able to move forward.

What is your opinion? What was your rating when you read it, and how many years ago was that?

#5
Certainly not infinite. There are 10^40 legal and sensible chess positions with no excess promotions. Most of these contain no tactics. Of those that contain tactics, they can be lumped together by common theme, like pin, discovered check, skewer, 7th rank, 8th rank, promotion...
ECO lists 500 opening variations A00 to E99, but that has no relation with the number of tactics. The same tactic say 8th rank can arise from almost any opening.

#7
In my opinion the book is marvellous and Nimzovich was a genius. I read it for the first time in 1974 and my rating was around 1700 then. Whenever I re-read it, I appreciate it more.

I definitely plan to read both of his books before I reach 1700.

I have 6 books that are all said to be "above my level" - My System, Chess Praxis, World's Greatest Chess Games, Judgement and Planning in Chess, Understanding Chess Middlegames, 100 Endgames You Must Know Workbook. All of them are books that I appreciate more as I gradually get stronger at playing chess.

#10
You can lay aside 'Chess Praxis' until after you have read 'My System'. You do not need to read the whole "My System": part 2 is more advanced, but part 1 is elementary. Of all 6 books you mention 'My System' is surely the best.

My System (Nimzovich) was very good, but Pawn Power in Chess (Kmoch) was a work of genius.

Where does Dan Heisman say this? Does he offer additional explanation?

Most people who have made lists of tactical ideas top out at a few dozen. Of course, each idea manifests itself in endless variations.

http://chessskill.blogspot.com/2012/04/tactical-motifs-list.html

There is no explanation at al!

It is just mentioned in passing here: https://www.danheisman.com/recommended-book-lists.html

"A set of tactics books which together may contain 97% of the ~2,000 basic tactics patterns (*= good three to start):"

The Polgar book "Chess: 5334 Problems, Combinations and Games" hints at 5334 patterns

That book contains about 3,500 mate in two problems. Many of those will be recognizing the same tactical pattern in a slightly different position.

Near the bottom he credits David Preuss and offers a dead link.

Google took me to a discussion on ChessTempo ten years ago that mentioned 2000 exercises.

I’m curious why Heisman uses the term patterns there.

There is something deeper that he is hinting at than the repetition one finds in the books he lists for beginning tacticians (I have and have used most of them in my teaching).

Perhaps he has in mind the several unnamed ideas I picked up when I spent a weekend looking at 100 games that all featured a kingside pawn storm against a castled king. These games, selected for the pawn structure, came from both Sicilians and Frenchs. At the time I was playing the Black side of the French against an NM. In these ~100 games, I found that after a pawn sacrifice on g6 by my opponent, I should first capture with the f-pawn. In the resulting structure with my opponent’s heavy pieces penetrating on the h-file, my king found sanctuary on f7 shielded by doubled pawns on g7 and g6. I suppose there are several patterns in that battle that I dimly understand now, and understood better a few years ago.

The mating motif on the other side of the board where I sacrificed my rook for the pawn on a3 has occurred many times since.

50 hours of puzzles where? On chess.com?

All of the puzzles here seem to involve very forcing moves. There are no puzzles, for example, the end in a quiet move and your opponent is in zugzwang. I had a book where the majority of puzzles were like this. You sacrifice, play some forcing things, then a nice quiet move to finish it off.

I also had a book where the majority of puzzles started with a large sacrifice (like rooks takes pawn).

Pins, forks, skewers are one thing, but I've noticed there are these different "flavors" of puzzles, so to speak.

Anyway, I imagine Heisman (or whoever he was referencing) was talking about standard manifestations of patterns. For example the Nc7 fork, or a Qa5 fork. These are patterns worth remembering because they happen over and over.

#19 mostly puzzles on chess.com but also some puzzles from books, some puzzles on chesstempo, some tactical sets on chess factor, and the chess tactics pro app.

I have seen zugzwang puzzles on chess.com, there is a wide variety of types across the whole database, but as you say the most common ones involve forcing moves and the other ones don't come up as often. 

Heisman has a book called "Is Your Move Safe?" it is a sort of a puzzle book but with all the puzzles based on move safety and not all of the solutions are black and white, some positions are more gray areas. I am fine with that because that reflects chess, but it isn't to everyone's taste.

That's my hunch, too.