1. Introduction
In the twentieth century, there were crises in mathematics, which led first to its complete axiomatization (in particular, axiomatic set theories appeared), and then to the famous theorems of Gödel on the incompleteness and impossibility of proving the consistency of an axiomatic theory by means formalized within the theory itself, and to the outstanding proofs of Gödel and Cohen that the generalized continuum hypothesis does not depend on the axioms of ZFC (the most popular axiomatic set theory), see [1]. That is, it cannot be either proven or refuted in ZFC (if ZFC is consistent).
The general opinion of mathematicians now boils down to the fact that Peano’s arithmetic is certainly consistent, and set theory is almost certainly consistent. This point of view actually means a rejection of the principle of scientific knowability, which Hilbert, apparently considered the most important principle in the work of a scientist.
The papers [2] [3] are devoted to proving that existing axiomatic set theories (in particular, ZFC theory) contain a contradiction. The present paper completes these articles, filling the gap in the proof at the end of [3]. Accordingly, the present paper assumes that the reader is familiar with the papers [2] [3]. In particular, all the notations used in the paper are borrowed from [1] [2]. The numbering of lemmas and theorems given in these papers is also preserved. To help the reader, a list of notations (common to all three papers) is given at the end of the paper.
It should be noted that the study of the inconsistency-consistency of existing axiomatic set theories has a meaning that goes far beyond the framework of “mathematical purism”. In fact, this question has a deep general mathematical and even physical, meaning. In connection with the latter, see, for example, the work [4], where set theory is used in models describing the phenomena of quantum physics.
2. Completion of the Proof of the Inconsistency of Set Theory
To make the reader’s work easier, we will first give a brief summary of the main results obtained in the works [2] [3]. The brief summary will allow the reader to better navigate the material presented in these works.
The concept of a tree and the operation of cutting trees are introduced. A tree contains vertices at each level except possibly the upper one. If an ordinal
denotes the level with the number m in a tree
, then
means the tree obtained by cutting
at the level
.
The concept of a strange tree is introduced as a tree
without through paths in which from each vertex
at level
there is a path to some vertex
of any level
less than the upper one, and considerations are given due to which the tree
is indeed strange (not consistent with intuitive ideas). It is shown that for
strange trees
of height
do not exist, but there is a strange homogeneous tree
. Theorems 1 and 2 are proved. By theorem 2 (theorem 1 is a weakened version of theorem 2), for each almost homogeneous tree
of height
(in particular,
can be a strange tree), there exists a through almost homogeneous tree
of height
that is almost isomorphic to
. If
, then
is not isomorphic to
, but is almost isomorphic to it.
Almost isomorphism means that the trees
and
(cuts of trees
and
at level
) are isomorphic for
. Theorem 2 underlies the approach to proving the inconsistency of set theory developed in [1] [2]. If it is proved that the isomorphism of
and
for all
implies the isomorphism of
and
, then a contradiction in set theory will follow from this.
A tree
is called homogeneous if for each two of its vertices
at level k the trees generated by them are isomorphic.
A tree
is called almost homogeneous if
is homogeneous for
, where
is the height of the tree.
Next, we introduce a class-set of almost through almost homogeneous trees of height
(notations:
,
, etc.) almost isomorphic to each other, including, together with the trees
, their cuts at any level
:
,
, containing both trees without through paths and with through paths (called the first class). By theorem 2, the first class of trees exists. We introduce trees with double vertices
, representing isomorphisms of the trees
,
(and, for simplicity, identified with them). A tree
is fixed and various overlays (isomorphisms) of
(and their cuttings) are considered.
For each two trees
from the first class of height
, the tree of overlays (isomorphisms)
is introduced, whose vertices at level
are all possible isomorphisms
. Thus, the second class of trees is introduced into consideration - the class of trees of isomorphisms of trees of the first class. In this class, there are also trees without through paths, as well as through trees. The former are obtained if we take two non-isomorphic trees of the first class of height
, and the latter - in all other cases. For
, the tree
is always through and homogeneous.
As it was said already, the tree
is fixed as a tree on which trees
of the first class are superimposed (when this can be done). For each level
in
, a numbering of automorphisms
is fixed in a certain way and a notation
is introduced for numbered automorphisms. We assume that
is the identity automorphism, and
for
is a non-final automorphism. An operation of multiplication of the isomorphism
by the automorphism
is introduced, the result of which is a new isomorphism.
For each
, we choose some non-final isomorphism
as the main isomorphism for a given
and give it the number 0. After that, we introduce the numbering of vertex-isomorphisms:
. In this case, we will have:
and
.
Each numbering is determined by the choice of
. The introduction of a numbering allows us to place the isomorphism trees
on the plane of places in various ways. We assume that when placed on the plane of places, the isomorphism
is imposed on the place
. The same applies to
.
The fundamental property of an isomorphism tree
is the property reflected in lemma 25.
Lemma 25. The isomorphism tree
satisfies the decomposition rule:
.
Also
.
Lemma 25 implies lemma 27. The last lemma plays a significant role throughout the paper.
Lemma 27. Let
be a sequence of numbers for which
. For isomorphic
there exists a through tree
for which
is a through path. By specifying a pair
, where
is a non-final isomorphism, the tree
is uniquely determined.
Let a sequence of place numbers
be given. If the isomorphism tree
has a through path
, then we say that
determines this path. For
,
, and
for non-final
, determining non-final paths
. The operation of multiplication of places
by automorphisms
is introduced:
,
, in which the sets
,
and
are trivially isomorphic with respect to the operation of multiplication of set elements by
.
Let
denote the continuing sequence of automorphisms
imposed on the plane of places. By definition,
, while
.
,
. In the continuing sequence of automorphisms
, all
for
are non-final. If
is not final, then
will be called non-final. Otherwise, we will talk about final
. Also by definition,
if
,
. The multiplication operation “×” turns the set
into a group, and the set
into a subgroup of this group.
The sequence
is a continuing sequence of identical automorphisms.
Lemma 29. For any non-final sequence
there exists a through tree
for which
defines a strongly through path
. If
defines a path
in the tree
, then
defines the path
.
Each through tree
is uniquely determined by the set of its through paths
, and each path is a continuing sequence of tree vertices. Therefore, it is convenient and clearly to characterize the order relations in a tree using through paths and keeping in mind that each sequence
is completely concretized by its upper term
:
.
The vector notation of the decomposition rule (see above) provides great convenience for a more compact formulation of the results. This notation is reflected in lemma 30.
Lemma 30. Let
be a path in
. Then
is a path in
if and only if
is a continuing sequence of automorphisms (
) for all
.
We will call the sequences
defining paths
in the tree
the prototypes of these paths. Due to the presence of the trivial isomorphism discussed above, this name is justified, and we can treat the prototypes of paths in almost the same way as the paths themselves. In particular, we have: if
is the prototype of a path, then
is also the prototype of a path. The following two lemmas are true, emphasizing the significance of the introduced concept of “being the prototype of a path”.
Lemma 31. Let
be the prototype of a non-final path in a through tree
. Then
, when
runs over all sequences (non-final sequences) of automorphisms, forms the set of all prototypes of paths (non-final paths) in
. Given
and a non-final isomorphism
, their collection uniquely determines a tree
for which
is the prototype of a through non-final path, and the isomorphism
is placed on
.
Lemma 32. Let
be the prototypes of through non-final paths in a through tree
. The one-to-one correspondence
, when
runs over all continuing sequences of automorphisms, defines a strong automorphism of the tree
under which
goes to
. Conversely, every strong automorphism of the through tree
is determined by the pair of prototypers of non-final paths
according to the formula
, when
runs over all continuing sequences of automorphisms. Fixing
and varying
(or vice versa) yields all existing strong automorphisms of
.
It is easy to see that the situation is similar if in lemma 32 the prototype of the through path
is replaced by the through path
itself, and the correspondence
is replaced by the correspondence
. Lemmas 31 and 32 characterize the situation with automorphisms of the tree
and play a fundamental role in the work.
We will call sequences of places
related if
with some
. We will call them strongly related if
with some non-final
. We will talk about classes of related (strongly related)
, meaning non-complementable sets of sequences of places
that are related (strongly related) to each other. We will introduce the notations
and
for the classes of related and strongly related sequences of places. The set of non-final sequences of places is one of the classes of strongly related sequences. We will give a special notation to this class -
. For non-limit
we assume that
.
.
. The operation of cutting preserves the relationship to be related and strongly related: if
are related (strongly related), then
are also related (strongly related).
The order relation between places in
induces a through tree of places
for which
is simultaneously the set of through paths and the set of prototypes of through paths. For
,
is always isomorphic to
.
Lemma 36. For a given
, any class of related sequences of places is a union of disjoint classes of strongly related sequences:
,
, если
.
The definition of related (strongly related) sequences can be preserved for the case where
it is taken instead of
(
is the limit ordinal). In this case, the analogue of lemma 36 is satisfied.
Lemma 37. For every through
, the set of prototypes of through paths is a class of related sequences of places.
Lemma 38. For any
and isomorphic
, there exists a through tree
for which
is the set of prototipes of through paths.
The concept of a continuing sequence
is introduced in a natural way.
continues
for
if
.
In [3] it is proved
Lemma 43. Let
be a tree of isomorphisms imposed on the plane of places. The tree
introduces a continuing sequence
in which each
is the set of prototypes of through paths of the tree
.
An immediate consequence of lemma 43 is
Theorem 4. Among the continuing sequences
there are both sequences with through paths and sequences without through paths.
Therefore, if it is proved that a continuing sequence
without through paths does not exist, then the inconsistency of set theory will follow.
We assume that the mathematical objects under study, the trees of isomorphisms
, are located on a section of the homogeneous plane of places (see the beginning of section 4 in [3]). This placement is determined by specifying for all
the numbering of isomorphisms
, where
is the i-th automorphism of the tree
, and is therefore entirely determined by the choice of the main isomorphisms. We assume that
and
are superimposed on
.
For greater clarity (specifying what was said in [3]), we will assume that for each tree
for each
, a primary numbering
is first introduced and fixed (simply as a way of denoting different isomorphism trees), and the secondary (working) numbering
is determined through the choice of the main isomorphism
,
. When we speak about a tree
imposed on the plane of places, we mean that it is imposed in accordance with the introduced working numbering of isomorphism trees. For different working numberings (with different choices of
) different superpositions will take place. Of course, the primary numbering can be considered as a special case of the secondary (with
).
The superposition (imposition) of
on the plane of places defines some isomorphism of
on the tree of places
, where the set of through paths in the tree of places
is the set of prototypes of through paths in
, and is determined by the working numbering of the vertices in the tree
. By the disposition of
on the plane of places we mean the set of all possible superpositions of
for the same set
of prototypes of through paths of the tree
. The disposition is uniquely determined by specifying any one of the impositions, the set of which forms it. The asignment of the sequence of main isomorphisms
uniquely determines some superposition and thereby determines some disposition
on the plane of places. The disposition
continues the disposition
if and only if the set
defining the disposition
continees the set
defining the disposition
.
Let there be a continuing sequence of sets of related sequences of places
. The tree
for
can always be strongly imposed on the set
in different ways, the totality of which determines the disposition of
on the plane of places, for which
is the set of prototypes of through paths of the tree
(lemmas 32, 37). In this case, we will speak of an
-disposition. Each continuing sequence
determines a continuing sequence of
-dispositions of
on the plane of places (see [3]).
Let us move on to the final part of the article. We want to prove that any continuing sequence of sets of related sequences of places
has a through path. This will imply a contradiction in set theory (theorem 4).
Let
be isomorphic to
and
be a through homogeneous tree. Let
be the set of through paths in the tree
.
completely determines the tree
(and for simplicity can be identified with it).
Each (isomorphic) mapping of
onto
uniquely determines a mapping of
onto
and is uniquely determined by (any) leading pair
, where
. We denote this mapping by
. In this case, we have the following individual path mappings:
(see lemma 32). If we fix
and allow
to take on all admissible values, we obtain the mappings
,
, covering all possible
-mappings. Therefore, we obtain a
-disposition of
on the plane of places. For clarity, we note that we regard trees obtained by mapping trees onto other ones as trees with double vertices (see section 3 of [2]). In view of what was said above, we can also speak of trees with double paths. A mapping of
onto
continues a mapping of
onto
if and only if the double paths of the first mapping continue the double paths of the second one. This means that if in the first mapping the path
is mapped onto
, then in the second mapping
is mapped onto
.
Note that in a similar way, each (automorphic) mapping of
onto itself uniquely determines a mapping of
onto itself (an automorphism of
) and is uniquely determined by (any) leading pair
, where
. In this case, the following individual mappings of paths take place:
.
Recall that we assume (and this does not reduce the generality of the results) that in the trees
at all levels with non-limit,
there are no final vertices. So, at these levels
. Thus,
it can only take place in the case of limit
.
Let
and a non-final continuing sequence of place sequences
be fixed. The sequence
defines mappings of
on the place plane
, where
varies, taking values less than
. In the mapping
, the leading pair is the pair
. The set of these mappings forms a disposition of
on the place plane, where
. Note that pairs
with different
belong to different impositions. Next, we introduce in an admissible way a sequence of places
, continuing the sequence
(this means that we add
to
with
). As a result, we obtain the superpositions on the plane of places
,
, continuing the corresponding superpositions
,
. Consequently, we obtain the disposition
on the plane of places, continuing the disposition of
.
At the same time, for any
-disposition, taking any non-final sequence
, we arrive at the same
-disposition.
It is easy to see that this consideration will cover all dispositions of
on the plane of places and all cases where the disposition of
continues the disposition of
.
The same holds when
is a limit ordinal and all continuing sequences of dispositions of
on the plane of places have already been constructed. An admissible sequence of places
generates a class of related sequences of places
. Let
continue
in an admissible way (this means that we add
with
to
). Then
generates a disposition of
, which continues the disposition
generated by
. For clarity, note that the choice of
determines the choice of a class of non-final strongly related sequences of places
, the continuations of which form a set
, which has the final part in
.
The above considerations make convincing the assertion that every continuing sequence of dispositions
is generated by some continuing sequence of places
and hence has as its limit some disposition of
on the plane of places determined by the sequence
, which is the limit of the sequence
. Therefore, every time the continuing sequence of sets
(determining some continuing sequence of dispositions
) has a through path, and we obtain a contradiction in set theory.
3. Conclusion
The work presented in this article complements the works [2] [3], filling the gap contained at the end of the work [3]. All steps of the proof in these works are based on generally accepted informal set-theoretic reasoning, but take into account the prohibitions that were included in axiomatic set theories in order to overcome the difficulties encountered by the naive Cantor set theory. So, due to these works, existing axiomatic set theories (in particular, ZFC theory) are inconsistent.
List of Basic Notations
—tree obtained by cutting tree
at level
(has height
);
—height of tree
;
—place with number
in row with number
on plane of places;
—automorphism of tree
with number
in primary numbering;
- notations for trees;
,
—tree of height
and tree obtained from
by deleting vertices of the upper level
;
—tree of height
with vertices
;
—tree representing isomorphism of trees
and
(double-vertex tree);
—isomorphism tree for trees
and
(at level
, tree vertices are trees
representing isomorphisms of trees
and
);
—automorphism tree for tree
;
when
—continuing sequence of trees;
means that
;
—a strange tree from section 4 [2];
—continuing sequence of vertices (path) in the tree
: for all
with
holds;
—the vertice with number
at level with number
in the tree
;
—the set of through paths in the tree
under consideration (gives a complete picture of the tree
and can be identified with it);
—the path with number
in the set
.