A summary of Weiss's main points, as far as relevant to the purpose of this blog, follows.
Emphasis is largely mine. This is a long article, from which I retain the headings of the sections.
It will be split in several postings.

* In references to the author's publications in the text, abbreviated to "P.W."


Introduction: need for the systems concept


Weiss stresses the need for the scientist to periodically step back
from his detailed work and have a look at what others in science
are doing in order to retain a sense of perspective and proportions.

His conclusions and postulates are derived “from pragmatic insights acquired
from the study of living organisms.” He wants to contribute to the marriage
of inductive experimental fact-finding and theoretical speculations
to bring forth something fruitful.

His prime object here is to document that a number of basic controversies
about the nature of organisms and living processes, “(e.g., reductionism versus
holism), readily vanish in the light of realistic studies of the actual
phenomena, described in language uncontaminated by preconceptions”.

“In this light (1) the principle of hierarchic order in living nature
reveals itself as a demonstrable descriptive fact, regardless of the
philosophical connotations that it may carry.”

and (2) there is a compelling necessity to accept organic entities as systems
which are subject to network dynamics, “rather than as bundles of micro-precisely
programmed linear chain reactions”. A strictly mechanistic, machine-like, notion
of the nature of living organisms “presupposes a high degree of precision
in the spatial and chronological program according to which the innumerable
concurrent component chains are composed and arrayed” to “keep the bunch
of separate processes from falling apart when faced with the fortuitous
fluctuations of the outer world”.


Animal behaviour: systems dynamics

Jacques Loeb (1918) explained animal behaviour in terms of
“concatenated reflex sequences”, and “particularly his proposition
of tropisms as paradigms of a precise cause-effect machine principle in
organisms, epitomizes that kind of mechanistic preconception”.
His thesis had two serious flaws. Firstly, that brand of naively mechanistic
thinking already had become outdated in physics;
secondly, “studies of the actual behavior of animals in goal-directed
or other forms of directional performances showed none of the presumed
stereotypism in the manner in which animals attained their objectives.”

“True, the beginning and end of a behavioral act could often be
unequivocally correlated with a vectorial cue from the environment; but
the execution of the given act was found to be so variable
and indeed unique in detail, from case to case and from instance
to instance, that it was gratuitous to maintain that the attainment
of essentially the same result regardless of the variety of approaches
is simply the blind outcome of a chain of seriated steps appropriately
pre-designed by evolution to lead to that end.”

So, organisms are “not puppets operated by environmental strings”;
moreover, the analogy is meaningless, because the "environment"
that pulls the strings of puppets in proper order is often another organism
with his brain.

Weiss' detailed study of the movements and tracks of butterflies
assuming resting postures prompted him to disavow the reflex chain theory
of animal orientation as unrealistic.
He proposed in its stead a general systems theory of animal behavior.
(P.W. 1925). The basic tenets of the paper seem to have been largely borne out
by later developments. That conceptual framework is set forth here.


Analytic thinking - an abstraction

To Weiss, the Universe presents itself as an cohesive continuum.
However, most of us are used to looking at it as a “patchwork of
discrete fragments. This habit stems partly from a biological heritage,
which makes focusing on 'things', such as prey, enemies, or obstacles, a
vital necessity”; our cultural tradition plays a role too; and curiosity,
“which draws our attention and interest to limited 'objects'.”
These can be:

• well-delineated patterns in our visual field;
• repetitive arrays of sounds in bird song, melody or human language;
• processes of patterned regularity, such as waves.

Their reiterative appearance in relatively constant and durable form
makes them the focus of our attention; we give these a name,
while the rest is simply "background". These named processes and patterns
are mentally dissected out because we happen to be especially interested
in these 'things' or have drawn our attention.They cannot be said
to be truly isolated or "isolable" from the rest. [See Whyte, 1949]

The process through which we have come to treat a 'cluster of properties,
called "parts", as ideally isolated, is mostly empirical'.
We think that 'objects' are independent of their environment,
but this is our perception. The latter refers to the limited powers
of discrimination of the observer and his instruments;
Also, in speaking of "independence from the environment",
we must allow that 'since "environment" is ubiquitous, we cannot test,
hence never discount, "dependencies" upon any of the features of the cosmic
environment which are universal'.

Weiss mentions temperature or radiation as cases in point.
Independence is not absolute, for all those “putatively independent entities
are interconnected by the common environmental matrix,
in which they lie embedded”.
Those so-called “discrete items”, form part and parcel of each other's environment.

To summarize this part: we have a habit of atomizing the Universe mentally
into isolated parts. But we do also see connections between isolated items,
and then sort those we deem "relevant" from "negligible" ones;
this “obviously lets the judgment of the describer (or of
statistics) intrude into purportedly "objective" descriptions
of properties of 'objects'”.