Two Conflicting Principles

I’m trying to improve my play by learning and following general principles. I’ve learnt two that in some games will be in conflict: (1) Try to exchange pieces (but not pawns) if you have a lead in development. (2) Don’t trade one of your active pieces for one of your opponent’s more passive ones (of same value).

Often if I have a small lead in development (e.g. one pawn), I will try to follow (1) and offer or try to force the trade of all pieces on the board. I know it will depend on every unique position, but should (2) in general overrule such an attempt at an exchange race?

There is no such general principle as (1), but (2) is correct. Perhaps you mixed up (1) with this correct one: Try to exchange pieces (but not pawns) if you have a lead in material. The idea is that if you are well ahead in material, try to simplify to an ending where your extra pieces become dominant, but keep the pawns around to retain more promotion options.

If you have a lead in development, the general principle is to open up the position to activate your line-pieces, typically by exchanging (or sometimes even sacrificing) pawns. A development lead is a temporary advantage that you want to maintain by going on the offensive, or convert to a permanent material advantage. 

This is the most important sentence in this thread. The opening poster has confused something with something else.

@1

"(1) Try to exchange pieces (but not pawns) if you have a lead in development"
++ This should be: 
'(1) Try to exchange pieces (but not pawns) if you have a material advantage'

"(2) Don’t trade one of your active pieces for one of your opponent’s more passive ones (of same value)." This is true, and also 
'trade one of your passive pieces for one of your opponent’s more active ones (of same value)'

"Often if I have a small lead in development (e.g. one pawn)"
++ One pawn is not a lead in development, it is a material advantage.

"I will try to follow (1) and offer or try to force the trade of all pieces on the board."
++ Yes, if you have a material advantage of 1 pawn it is good to trade pieces, not pawns.

"should (2) in general overrule such an attempt at an exchange race?"
++ It is not an exchange race, it is simplification to a won endgame with the aim to queen the extra pawn. Think of the pawn as a queen to be. (1) overrules (2). If you can queen an extra pawn, it is worth trading your active pieces for your opponent's passive pieces.

Yes! One pawn advantage means nothing if your opponent has better piece activity, mobility, centralization, infiltration, and/or connectedness.

Only in a balanced position it will be wise to stir up exchanges if you are a pawn up.
You have to calculate that you can actually do something with that extra pawn down the line and you can maintain the advantage.

Also if his/her pawns are more advanced, your material advantage is likely to get dissolved.
A pawn two squares from promoting is worth about a piece in value, and becomes worth roughly a rook one square from promotion (since you'll often have to sac a rook for it)

It also depends on how your pieces can make use of your pawns. Can you form outposts, are your bishops blocked or facilitated by the pawn structures?

Note that chess principles are inherently conflicting, because it depends on the specific situation.
Same with early castling - it doesn't always ring true.

You don't need to just learn the user manual for an airplane to be able to fly - you need to become a good pilot.

THIS.  It is important to stop and make sure you understand these terms.  A "lead in development" means that you have brought out more of your pieces than your opponent.  A "material advantage" means you have captured more pieces than your opponent has captured.  These are two very different things.

All else being equal, if you have a lead in development, you should NOT exchange pieces - that would reduce the pressure - instead you should continue developing and start planning how to take advantage of your lead in development to initiate an attack.  If, on the other hand, you have a material advantage, then trading is good because it can lead to a winning endgame.  Also the ratio of your material advantage increases as the number of pieces on the board decrease.

For instance, a typical progression is to try and get better development, then use that development to initiate an attack, then when the attack succeeds and you win some material, start trading pieces to turn that material advantage into a winning endgame.

Analyse such games with an engine and see whether the engine agrees with your decision to trade (or not to trade) pieces. There isn't a simple fix for your situation and it takes skill and experience, it takes time to get better at this. 

Edit: I misread your question as "if you are up a pawn" instead of "if you are up in development". I have never heard about the principle that you should exchange pieces if you are up in development. Sometimes exchanging your opponent's only active piece while being up in development is a good idea though. 

Thanks for all the replies and tips.

As many of you have pointed out, I wrote “lead in development” where I meant “material advantage”. English is not my native language – although I will certainly not repeat that particular error. I am sorry for the confusion caused by the mistake.

I’ll follow dude0812’s advice and use computer analysis to investigate the relation between the two principles in various situations in my own games.

I misread your comment and I actually read it the way you wanted to write it. I did it because the rest of the comment only makes sense if you are talking about being up material. All else being equal you should trade, but be careful, sometimes trades can drastically worsen your position (sometimes they can improve it as well). As I have already stated, there is no magic formula for this, getting better at this requires practice, experience, analysing your decisions and seeing whether they were correct and if they were wrong analysing why they were wrong.

@fartein -

I suggest to get the following book and read the chapter 'Exchanging Pieces' (pages 80-92). The book clearly explains everything you have enquired about, along with many other essential chess fundamentals, principles and techniques...

Weapons of Chess by Bruce Pandolfini

https://www.google.com/books/edition/Weapons_of_Chess_An_Omnibus_of_Chess_Str/A6c6jzJkMj4C?hl=en&gbpv=1&dq=weapons+of+chess&printsec=frontcover

I also comment on that book here....

Good Chess Books for Beginners and Beyond...

https://www.chess.com/blog/RussBell/good-chess-books-for-beginners-and-beyond

Principles in general are just a guide. Use them loosely. They are meant to help you make a judgement between otherwise equal looking moves and to guide you to the correct candidate moves. Your plan shouldn't be to exchange pieces just because you won a pawn, rather a plan that leads to exchanges might be superior to a plan that complicates the position. However, as you note there are definitely other factors at play in any given position.

@11
So rephrase your 2 principles:

(1) If you have a material advantage, then exchange pieces, not pawns.

(2) If material is equal, then exchange your passive pieces for his active pieces
and do not exchange your active pieces for his passive pieces.

Exchanging active for passive pieces should always be carefully considered, many times it is not idea to do so even if you are up material, especially if you are only up a pawn. Of course, this depends on how much material you are up and on the exact position, it has to be decided on a case by case basis. One bad trade can give up all the advantage or even lose you the game.

@16
"if you are only up a pawn"
++ 1 pawn is enough to win a game: create a passed pawn, queen it, checkmate.

I've often thought like this. If I manage to get to be up a pawn, and keep trading to simplify and keep the material advantage, I'll win be queen (or rook) promotion. Keeping the material advantage does not allways work out according to plan though

Thanks for the tip, RussBell

That's not how chess works. There are billions of positions where one side is up a pawn yet the position is drawn or even losing for the side that is up a pawn. Mindlessly trading when you are up just 1 pawn is a horrible advice.

A conto what we are talking about here, today I had a game in which I was up a pawn and by making one bad trade I lost the advantage (later in the game my opponent gave me back the advantage then I lost it again, then my opponent blundered again so I won, but that's irrelevant for this discussion).

Here is the position. I am playing black and I played Bxb3 and then exchanged a pair of rooks as well. Evaluation went from -3 to -0.5 (from a winning advantage to a drawn position).

tygxc is giving you horrible advice. When you are up only 1 pawn you can make 1 bad trade and turn a winning position into a losing one. tygxc philosophy of being married to material is demonstrably and objectively wrong. Engine evaluations clearly show that there are tons of positions where the position is equal or where you are losing despite being up a pawn. A bad trade can cause a lot of damage. The more material you are up the less bad trades are likely to hurt you. When you are up only 1 pawn you must be very sure that the trade that you are making is ok. I wouldn't put the fact that I am up a pawn on top of my priority list when deciding whether to make a certain trade or not. Today I played a game in which I ignored this advice and my move to trade pieces because I was up a pawn was horrible, it gave away the winning advantage. You can see my previous comment to see what I am talking about.

@20
A bishop is worth more than a knight. ...Bxb3 is not an even trade.

@21
'Other things being equal, any material gain, no matter how small, means success' - Capablanca