I cannot tell a lie ...
Words fail us.

We cannot tell the truth because words are imprecise tools for the job. Words have multiple meanings, meanings we often do not care to have included when we attempt to express our thoughts.

Write a book. Suppose your book is of average length, between 200 and 300 pages. Most of it will consist of the same 750 or so words, repeated in a variety of different ways. Yet English, with about 650,000 words to choose from in the active language, gives us many alternatives to choose from.

Many of those core words, so vital to communication, are general purpose tools, like 'it'. They are vague and misleading. "My wife took the dog for a walk and she hurt her foot". Whose foot got hurt? Who caused the pain? There are four different ways it could go, assuming the dog is female.

So we can only approach the truth of a thing by sketching it loosely with words, then correcting the possible misinterpretations, then filling in details, until we fill in a picture of the truth by a series of successive approximations.

It is much simpler to tell lies.