What is the difference between an infinitive and a gerund as subject of a sentence? [duplicate]

Question

To run is good
Running is good

What is the difference in meaning?

Answer 1

The infinitive and the gerund do not mean the same thing. (Source), (Source), (Source) They are not interchangeable because there is a semantic difference between them.

Contrary to popular opinion, the infinitive, unlike the gerund, has a tense aspect:

Infinitives have a tense operator which fixes the understood time frame of the complement clause relative to the tense of the matrix [main verb] This tense conveyed by the infinitive is that of a possible future, or something hypothetical or unrealized. [Stowell, 1982, p. 562] http://www.jstor.org/stable/4178293.

Although not inflected, the idea of futurity is built into the infinitive, irrespective of how it's used.

Infinitives as adjectives:

something to do.

a place to go.

things to come.

In these noun phrases the infinitive adjective expresses the idea of the future, of things yet to happen. Notice that saying "things to come in the future" is redundant because the infinitive "to come" already carries the idea of futurity.

The infinitive as an adverb of purpose/reason/result:

To pass this test, you need a grade of 60% or more

He came over to help out.

To lose weight, you need to work out consistently

The infinitive always expresses the idea of an unrealized possibility that is to happen in the future relative to the tense of the main verb.

So when using the infinitive as an abstract noun and choosing between it and the gerund, the difference is that the infinitive is meant to express unrealized possibilities while the gerund expresses the action in a general sense with no tense aspect or as an action that was already completed.

The infinitive as object/complement:

I want to learn

I tried to leave

They asked me to stay

Notice that the infinitive is an unrealized action, a possibility that may happen after the time indicated by the tense of the main verb.

The gerund as object/complement:

I like running

My first love is swimming

I gave scuba-diving a try

The gerund makes a generalized statement about the action, with no sense of time.

Sometimes the meaning changes depending on which you use:

(a) Bob remembered to bring the wine.

(b) Bob remembered bringing the wine

This example illustrates the difference between the infinitive and the gerund. The two sentences do not mean the same thing. In a, bob remembered that he had to bring the wine. The infinitive "to bring" was unrealized at the time he remembered. In b, the gerund "bringing" was completed in the past, which is equivalent to saying he remembered that he brought the wine.

The gerund or infinitive as subject

Running is good.

Grammar is fun.

These are general statements about the action. The gerund is preferred as the subject in the vast majority of cases.

The infinitive can be the subject but only when it expresses unrealized actions or actions to happen in the future:

"To be or not to be?".

Here "to be" is in question. It has not been realized.

“To plant a garden is to believe in tomorrow.” –Audrey Hepburn

In this example, the infinitive subject "To plant a garden" agrees with the complement "to believe in tomorrow", both actions to happen in the future. The sentence is stating that the prospect of planting a garden is equivalent to believing/hoping for things to happen in the future.

So to answer the questioner, the statement "To run is good." is not the right choice, and sounds bad. When making a general statement about the action you use the gerund "Running is good".