Our tour of grammar brought us recently (Riding the Rapids) into the fast-moving waters of participles and gerunds. And why not? We use these constructions a thousand times a day, and the more we know how they work, the better we can employ them. So at the risk of being swept away, let’s step farther out to understand the difference between a gerund and what is called an infinitive.
We agreed last time that a gerund is a verbal noun, which means nothing more than it is a noun constructed from a verb. Truth be told it’s an exotic creature in the waters we’re crossing, and it seems to have evolved from the realization that some things only exist when they’re moving: cooking, for example, or cleaning or writing or running. Stop moving your legs, and where’s the running? Start moving them again, and you can’t deny the reality of it. A gerund, then, names a kind of thing that lives only when it’s moving and vanishes for a time when it’s not, unlike other nouns that just stay put: pencil and paper, for example, or a pin or pot.
So what is the difference, then, between cooking and to cook? If I tell you that I love to cook, am I not saying the same thing when I say I love cooking? Logically yes, but what is the grammatical difference? We know now that cooking is a gerund: it is naming an action that we regard as a noun, something that exists only when it’s underway, and we can confirm that cooking is a noun when we see that it is the object of the transitive verb love: I love something, and what I’m saying here I love is cooking. We answer the question what? with a noun (or with what is more properly called a substantive, any grammatical element that is acting as a noun), and in this sentence the noun comes in the form of a gerund.
But to cook must also be a noun, because it too can answer the question what do you love? and stand as the object of the transitive verb love. So if to cook is a noun but not a gerund (it obviously doesn’t end with the suffix –ing), what kind of noun is it? In these mysterious waters lives another strange creature called an infinitive. Like the gerund, an infinitive also is a verbal noun, but look more closely and you can see that its verbal coloring, so to speak, is not quite so dominant. To say I love to cook points more to the idea of cooking than to the action of cooking, a shade of difference we can perceive if we add an object: I love to cook a big meal versus I love cooking a big meal. The scene is busier and livelier when the gerund is around, and a little more notional when the infinitive takes charge.
An infinitive, then, is another kind of verbal noun, but it has evolved the ability to do things the gerund cannot. A gerund must be a noun and only a noun; an infinitive can serve as a noun, but also elsewhere it can work as an adjective or adverb if needed. If I say that my grandmother instilled in me a desire to cook, the infinitive to cook is now working alongside the noun desire, so it must be acting as an adjective. And if I go on to say that I would be glad to cook for you, the infinitive to cook now modifies the adjective glad, which means it is acting as an adverb. Evolution is a marvelous thing.
Infinitives are found in deeper grammatical waters, and much more can be discovered about how they can transform themselves into clauses (my grandmother loved that I cooked so much) and even disguise themselves in other shapes (she watched me cook all the time). They play an indispensable role in the linguistic environment, and provide the informed writer with yet more choices in adapting sentences to fit their audience and purpose.