最終更新日：2025/12/05
A puzzle of this kind: You are given two indistinguishable envelopes, each containing money; one contains twice as much as the other. You may pick one envelope and keep the money it contains. Having chosen an envelope at will, but before inspecting it, you are given the chance to switch envelopes. Should you switch?
Because you stand to gain twice as much money if you switch while risking only a loss of half of what you currently have, it is possible to argue (fallaciously) that it is beneficial to switch.
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two envelopes problem
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元となった辞書の項目
two envelopes problem
固有名詞
A
puzzle
of
this
kind:
"You
are
given
two
indistinguishable
envelopes,
each
containing
money;
one
contains
twice
as
much
as
the
other.
You
may
pick
one
envelope
and
keep
the
money
it
contains.
Having
chosen
an
envelope
at
will,
but
before
inspecting
it,
you
are
given
the
chance
to
switch
envelopes.
Should
you
switch?"
Because
you
stand
to
gain
twice
as
much
money
if
you
switch
while
risking
only
a
loss
of
half
of
what
you
currently
have,
it
is
possible
to
argue
(fallaciously)
that
it
is
beneficial
to
switch.
日本語の意味
「two envelopes problem」とは、区別のつかない2つの封筒があり、そのうち1つにはもう1つの封筒に入っている金額の2倍の金額が入っているという状況が設定されたパズル（数学的・論理的な問題）です。1つの封筒を選んだ後、中身を確認する前に封筒を交換する機会が与えられ、交換することで理論上倍の利益を得る可能性がある一方、実際には矛盾やパラドックスが生じることを議論する問題です。
意味（1）
A
puzzle
of
this
kind:
"You
are
given
two
indistinguishable
envelopes,
each
containing
money;
one
contains
twice
as
much
as
the
other.
You
may
pick
one
envelope
and
keep
the
money
it
contains.
Having
chosen
an
envelope
at
will,
but
before
inspecting
it,
you
are
given
the
chance
to
switch
envelopes.
Should
you
switch?"
Because
you
stand
to
gain
twice
as
much
money
if
you
switch
while
risking
only
a
loss
of
half
of
what
you
currently
have,
it
is
possible
to
argue
(fallaciously)
that
it
is
beneficial
to
switch.
（ canonical ）
