What thoughts begin to enter Victor’s mind as he works in his laboratory?Frankenstein by Mary Shelley

In the remote Scottish village where Victor begins his
creation of a female companion for his "monster" with what he calls "a tremulous and
eager hope."  However, one night as the moon just begins its ascension from the sea,
Victor Frankenstein must take a break; as he does he begins to reflect upon what he is
doing:

Three
years before I was engaged in the same manner, and had created a fiend whose
unparalleled barabarity had desolated my heart, and filled it for ever with the
bitterest remorse.  I was now about to form another being, of whose dispositions I was
alike ignorant....

Victor
worries about what this female may become.  And, while the monster has sworn to leave
the area and never come around people, the female, if created, would not have made such
a commitment.  What could happen then?  Also, Victor wonders how his monster will react
if he must face one daily that resembles him.  Or, she might turn from him in abhorrence
if she is composed in a more pleasing fashion.  Then, the monster would again be alone,
and renew his revenge upon mankind. Carrying his thoughts further, Victor is anxious
about the couples' reproducing, if possible, and "a race of devils would be propagated
upon the earth" who could diminish the current species of man.  All these reflections
turn Victor from the "sophism" of the being he has already created.  He fears that if he
creates yet another, future generation will curse him as "their
pest."

When he trembles and looks up, Victor sees "the
daemon at the casement," who face,Victor feels conveys malice and treachery.  In a
passionate reaction, Victor tears to pieces the "thing" which he fashions.  The creature
outside witnesses this and "with a howl of devilish despair and revenge" he goes
away.

This passage is significant because in it
Shelley explores the debate of scientific discovery and its ramifications for humanity. 
Besides the sin of Victor as he presumes to create a being, there is also the question
of whether scientific discovery can always benefit man.  May it not hinder the soul, the
goodness in man as it substitutes for actions that should be dictated by the human
heart?