<p>Basically, what is the difference between "can" and "could."</p>
<p>As in:</p>
<p>In the fifteenth century, Leonardo da Vinci suggested that defective vision can be corrected by placing a lens in direct contact with the eye.</p>
<p>i believe this should be “could” but not sure why</p>
<p>“could” is past. “can” is present.</p>
<p>Interesting. So whenever someone says (in the present) something along the lines of “Well, we could go on a walk” it is incorrect?</p>
<p>Isn’t ‘could’ future too?</p>
<p>I wish I could get a 2400 on the SAT.</p>
<p>“could” isn’t being used in the future sense in your example. It’s being used in the subjunctive mood.</p>
<p>Ahh true… I see</p>
<p>BB’s explanation was really convoluted. I wish they could just say:</p>
<p>“could” is past. “can” is present.</p>