Last week, I clarified that the modals “will” and “can” are both present-tense forms that inflect in a grammatically similar way in the past tense—“will” changes to “would” and “can” to “could.”

Thus, “can” in the present-tense sentence “I can play the piano” becomes “could” in the past-tense sentence “There was a time when I could play the piano.” Also, the past-tense forms “would” and “could” are used in indirect speech when it’s introduced by a verb in the past tense: “The fallen boxing champion promised that he would avoid any more distractions in his boxing career.” “The clerics asserted that they could make the RH Bill voted out in Congress.”

Now, in reply to a subsequent question raised by Miss Mae, a member of Jose Carillo’s English Forum, we will take up the specific uses of “can” and “could.”

First, “can” is used to convey the ability or means, knowledge, money, or equipment to do something: “I can play the piano.” “I can do integral calculus.” “I can afford a weekend vacation in Hong Kong.” “They can haul all that trash in half a day.”

Second, “can” is used for declaring that you see, hear, feel, taste, smell, understand, or remember something: “We can see the valley from here.” “I can hear you loud and clear.” “I can taste a hint of cinnamon in this bread.” “We can still remember when Typhoon Trix demolished our house in 1952.”

Third, “can” is used for saying what can possibly be done: “We can go shopping anytime you want.” “We can go biking all day.”

Fourth, “can” is used for saying that it’s possible to do something: “With a smartphone, you can now surf the web while traveling.” “We can fly to Bangkok for less than $100 during off-seasons.”

Fifth, “can” conveys the idea of being allowed to do something or having the right or power to do something: “You can share my condominium unit if you want,” “No need for a travel agent; we can make our flight bookings ourselves online anytime.”

Sixth, “can” is used as a mark of civility or politeness when making spoken requests or when offering or suggesting something: “Can you tell me how to say ‘I love you’ in French?” “Can I offer you a ride home?” “Can I carry that shopping bag for you?” (This is as opposed to bluntly saying: “Tell me how to say ‘I love you’ in French.” “I want to offer you a ride home.” “I’ll carry that shopping bag for you.”)

“Can” in its negative form “cannot” or “can’t” is used for emphasizing that something should not happen or continue: “That’s something I cannot do under the circumstances.” “We can’t allow these religious charlatans to dictate what’s right or wrong.” The negative forms “cannot” or “can’t” is also used to express shock or surprise: “She can’t speak for me! How presumptuous of her!”

As I indicated at the outset, the modal “can” inflects to “could” when a present-tense sentence is rendered in the past tense: “I could do integral calculus when I was in college.”

“Before he got married, he could afford annual vacations in Europe.” “Before they put up those high-rise condominiums, we could see the valley from here.”

In spoken form, of course, “could” is used to make a deferential or more polite request, offer, or suggestion: “Could you tell me how to say ‘I love you’ in French?” “Could I offer you a ride home?” (Compare these to their likewise polite but less deferential equivalents using “can” that were given earlier: ‘Can you tell me how to say ‘I love you’ in French?” “Can I offer you a ride home?”)

Their usage may look complicated, but with constant practice, the choice between “can” and “could” should become instinctive to all of us.
 
Visit Jose Carillo’s English Forum at http://josecarilloforum.com. Follow me at Twitter.com @J8Carillo.
 
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