Each chapter in this book has an introduction, the first section. But there
is no introduction to the book itself. So, let me use the mask of the Preface
for this purpose. Of course, a plain introduction to the book is just to
place the book in your hand; but while you are reading it, you yourself
have already done that. Well done!
This is the way I will be talking to you throughout. I will ask you to
do exercises on the spot, often waiting for you up to some point, and then
give you a hint to proceed. It is something like the following commercial
for the book:
I would like to ask you three questions, would you answer them
with a plain ‘Yes’ or ‘No’?
Good, you have answered ‘Yes’, whatever be the reason. But
see, that was my first question. Would you answer the same to
the second as to the third?
Very good, you have answered ‘Yes’ again; of course, it does
not matter. If you have not bought a copy of this book, are you
going to buy it soon?
Look, if you have answered ‘Yes’ to the second question, you
are also answering ‘Yes’ to the third, and if you have answered
‘No’ to the second, you are not answering ‘No’ to the third, i.e.,
your answer to the third is undoubtedly, ‘Yes’. Excellent. That
is the end of the commercial.